From 0fb65791fd1309e34de8f343bbba8fd10b1e906e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Thu, 19 Jun 2025 11:07:17 +0200
Subject: [PATCH 01/15] update existing tests

---
 test/testtokenize.cpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index c2781a1fb03..f0659efe6ea 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -4724,7 +4724,7 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS("struct RGB { unsigned int r ; unsigned int g ; unsigned int b ; } ;", tokenizeAndStringify(code1));
 
         const char code2[] = "struct A { int a : 3; int : 3; int c : 3; };";
-        ASSERT_EQUALS("struct A { int a ; int c ; } ;", tokenizeAndStringify(code2));
+        ASSERT_EQUALS("struct A { int a ; int __cppcheck_anon_bit_field_0__ ; int c ; } ;", tokenizeAndStringify(code2));
 
         const char code3[] = "struct A { virtual void f() {} int f1 : 1; };";
         ASSERT_EQUALS("struct A { virtual void f ( ) { } int f1 ; } ;", tokenizeAndStringify(code3));
@@ -4738,7 +4738,7 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS("struct A { bool b ; bool c ; } ;", tokenizeAndStringify(code2));
 
         const char code3[] = "struct A { bool : true; };";
-        ASSERT_EQUALS("struct A { } ;", tokenizeAndStringify(code3));
+        ASSERT_EQUALS("struct A { bool __cppcheck_anon_bit_field_0__ ; } ;", tokenizeAndStringify(code3));
     }
 
     void bitfields7() { // ticket #1987
@@ -4789,7 +4789,7 @@ class TestTokenizer : public TestFixture {
 
     void bitfields12() { // ticket #3485 (segmentation fault)
         const char code[] = "{a:1;};\n";
-        ASSERT_EQUALS("{ } ;", tokenizeAndStringify(code));
+        ASSERT_EQUALS("{ a __cppcheck_anon_bit_field_0__ ; } ;", tokenizeAndStringify(code));
     }
 
     void bitfields13() { // ticket #3502 (segmentation fault)
@@ -4829,9 +4829,9 @@ class TestTokenizer : public TestFixture {
                             "};\n";
         const char expected[] = "struct S {\n"
                                 "volatile uint32_t a ;\n"
-                                "\n"
+                                "volatile uint32_t __cppcheck_anon_bit_field_0__ ;\n"
                                 "volatile uint32_t b ;\n"
-                                "\n"
+                                "volatile uint32_t __cppcheck_anon_bit_field_1__ ;\n"
                                 "} ;";
         ASSERT_EQUALS(expected, tokenizeAndStringify(code));
 
@@ -4841,7 +4841,7 @@ class TestTokenizer : public TestFixture {
                              "};\n";
         const char expected2[] = "struct S {\n"
                                  "const volatile uint32_t a ;\n"
-                                 "\n"
+                                 "const volatile uint32_t __cppcheck_anon_bit_field_0__ ;\n"
                                  "} ;";
         ASSERT_EQUALS(expected2, tokenizeAndStringify(code2));
     }

From 841c628b9bb7fdff359515f3d908073af0377460 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Thu, 19 Jun 2025 15:38:35 +0200
Subject: [PATCH 02/15] add valueflow test

---
 test/testvalueflow.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 86fa02b9191..d8d4913c5e1 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -9122,6 +9122,10 @@ class TestValueFlow : public TestFixture {
                       "int b : 16;\n"
                       "unsigned short c;\n",
                       8);
+
+        testBitfields("unsigned int a : 31;\n"
+                      "unsigned int   : 2;\n",
+                      8);
     }
 };
 

From 38aa42f18b20f1e97f6e165cef4046b4b2270db9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Thu, 19 Jun 2025 11:03:15 +0200
Subject: [PATCH 03/15] fix #13954

---
 lib/checkclass.cpp     |  3 +++
 lib/checkunusedvar.cpp |  3 +++
 lib/token.h            |  8 ++++++++
 lib/tokenize.cpp       | 17 ++++++++++-------
 4 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/lib/checkclass.cpp b/lib/checkclass.cpp
index 8c9cd789fc0..83bcc8b8e06 100644
--- a/lib/checkclass.cpp
+++ b/lib/checkclass.cpp
@@ -231,6 +231,9 @@ void CheckClass::constructors()
                 if (usage.assign || usage.init || var.isStatic())
                     continue;
 
+                if (var.nameToken() && var.nameToken()->isAnonymousBitfield())
+                    continue;
+
                 if (var.valueType() && var.valueType()->pointer == 0 && var.type() && var.type()->needInitialization == Type::NeedInitialization::False && var.type()->derivedFrom.empty())
                     continue;
 
diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index a01de5a87ca..687f5c5983b 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1575,6 +1575,9 @@ void CheckUnusedVar::checkStructMemberUsage()
             if (isInherited && !var.isPrivate())
                 continue;
 
+            if (var.nameToken() && (var.nameToken()->isAttributeUnused() || var.nameToken()->isAnonymousBitfield()))
+                continue;
+
             if (mTokenizer->isVarUsedInTemplate(var.declarationId()))
                 continue;
 
diff --git a/lib/token.h b/lib/token.h
index 59774747f70..bf6d0bc0f7d 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -742,6 +742,13 @@ class CPPCHECKLIB Token {
         setFlag(fIsInitBracket, b);
     }
 
+    bool isAnonymousBitfield() const {
+        return getFlag(fIsAnonymousBitfield);
+    }
+    void isAnonymousBitfield(bool b) {
+        setFlag(fIsAnonymousBitfield, b);
+    }
+
     // cppcheck-suppress unusedFunction
     bool isBitfield() const {
         return mImpl->mBits > 0;
@@ -1426,6 +1433,7 @@ class CPPCHECKLIB Token {
         fIsFinalType            = (1ULL << 42), // Is this a type with final specifier
         fIsInitComma            = (1ULL << 43), // Is this comma located inside some {..}. i.e: {1,2,3,4}
         fIsInitBracket          = (1ULL << 44), // Is this bracket used as a part of variable initialization i.e: int a{5}, b(2);
+        fIsAnonymousBitfield    = (1ULL << 45), // Is this a token added for an unnamed bit-field
     };
 
     enum : std::uint8_t {
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index d91e9e7c3b9..83f2c660baf 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -9985,12 +9985,8 @@ void Tokenizer::simplifyAt()
 // Simplify bitfields
 void Tokenizer::simplifyBitfields()
 {
-    bool goback = false;
+    std::size_t anonymousBitfieldCounter = 0;
     for (Token *tok = list.front(); tok; tok = tok->next()) {
-        if (goback) {
-            goback = false;
-            tok = tok->previous();
-        }
         Token *last = nullptr;
 
         if (Token::simpleMatch(tok, "for ("))
@@ -10040,8 +10036,15 @@ void Tokenizer::simplifyBitfields()
             }
         } else if (Token::Match(typeTok, "%type% : %num%|%bool% ;") &&
                    typeTok->str() != "default") {
-            tok->deleteNext(4 + tokDistance(tok, typeTok) - 1);
-            goback = true;
+            const std::size_t id = anonymousBitfieldCounter++;
+            const std::string name = "__cppcheck_anon_bit_field_" + std::to_string(id) + "__";
+            Token *newTok = typeTok->insertToken(name);
+            newTok->isAnonymousBitfield(true);
+            if (newTok->tokAt(2)->isBoolean())
+                newTok->setBits(static_cast<unsigned char>(newTok->strAt(2) == "true"));
+            else
+                newTok->setBits(static_cast<unsigned char>(MathLib::toBigNumber(newTok->tokAt(2))));
+            newTok->deleteNext(2);
         }
 
         if (last && last->str() == ",") {

From 5db961c16932b0f85699bc6e05563d1fb4b8de3b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Thu, 19 Jun 2025 11:14:03 +0200
Subject: [PATCH 04/15] add tests relating to struct members

---
 test/testconstructors.cpp | 11 +++++++++++
 test/testunusedvar.cpp    |  9 +++++++++
 2 files changed, 20 insertions(+)

diff --git a/test/testconstructors.cpp b/test/testconstructors.cpp
index b57d6d80305..39de3b1cf1d 100644
--- a/test/testconstructors.cpp
+++ b/test/testconstructors.cpp
@@ -172,6 +172,7 @@ class TestConstructors : public TestFixture {
         TEST_CASE(uninitVar33); // ticket #10295
         TEST_CASE(uninitVar34); // ticket #10841
         TEST_CASE(uninitVar35);
+        TEST_CASE(uninitVar36);
         TEST_CASE(uninitVarEnum1);
         TEST_CASE(uninitVarEnum2); // ticket #8146
         TEST_CASE(uninitVarStream);
@@ -3020,6 +3021,16 @@ class TestConstructors : public TestFixture {
         ASSERT_EQUALS("", errout_str());
     }
 
+    void uninitVar36() {
+        check("struct S {\n"
+              "    unsigned int a : 16;\n"
+              "    unsigned int   : 8;\n"
+              "    unsigned int b : 8;\n"
+              "    S() : a(0) {}\n"
+              "};\n");
+        ASSERT_EQUALS("[test.cpp:5:5]: (warning) Member variable 'S::b' is not initialized in the constructor. [uninitMemberVar]\n", errout_str());
+    }
+
     void uninitVarArray1() {
         check("class John\n"
               "{\n"
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index ac23e1e75f4..51e429019a6 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -70,6 +70,7 @@ class TestUnusedVar : public TestFixture {
         TEST_CASE(structmember25);
         TEST_CASE(structmember26); // #13345
         TEST_CASE(structmember27); // #13367
+        TEST_CASE(structmember28);
         TEST_CASE(structmember_macro);
         TEST_CASE(structmember_template_argument); // #13887 - do not report that member used in template argument is unused
         TEST_CASE(classmember);
@@ -1998,6 +1999,14 @@ class TestUnusedVar : public TestFixture {
                       errout_str());
     }
 
+    void structmember28() {
+        checkStructMemberUsage("struct S {\n"
+                               "    unsigned int a : 16;\n"
+                               "    unsigned int : 16;\n"
+                               "};\n");
+        ASSERT_EQUALS("[test.cpp:2:18]: (style) struct member 'S::a' is never used. [unusedStructMember]\n", errout_str());
+    }
+
     void structmember_macro() {
         checkStructMemberUsageP("#define S(n) struct n { int a, b, c; };\n"
                                 "S(unused);\n");

From 05125270221783c72e39e7444e5edc10458aa38c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Mon, 23 Jun 2025 10:58:06 +0200
Subject: [PATCH 05/15] add test for unnamed bit-fields of size zero

---
 test/testvalueflow.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index d8d4913c5e1..1d00d0b8133 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -9126,6 +9126,11 @@ class TestValueFlow : public TestFixture {
         testBitfields("unsigned int a : 31;\n"
                       "unsigned int   : 2;\n",
                       8);
+
+        testBitfields("unsigned int a : 16;\n"
+                      "unsigned int   : 0;\n"
+                      "unsigned int b : 16;\n",
+                      8);
     }
 };
 

From 4a392ca427247e0ad0c881b46f83e1a18e2efcdf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Mon, 23 Jun 2025 10:53:38 +0200
Subject: [PATCH 06/15] handle unnamed bitfields of size zero

---
 addons/cppcheckdata.py |  7 ++++---
 addons/misra.py        |  2 +-
 lib/symboldatabase.cpp |  2 +-
 lib/symboldatabase.h   |  2 +-
 lib/token.h            |  6 +++---
 lib/tokenize.cpp       |  6 +++---
 lib/valueflow.cpp      | 13 ++++++++++---
 7 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/addons/cppcheckdata.py b/addons/cppcheckdata.py
index 88a4d8cb157..a4257e2a3ed 100755
--- a/addons/cppcheckdata.py
+++ b/addons/cppcheckdata.py
@@ -166,7 +166,7 @@ class ValueType:
     Attributes:
         type             nonstd/pod/record/smart-pointer/container/iterator/void/bool/char/short/wchar_t/int/long/long long/unknown int/float/double/long double
         sign             signed/unsigned
-        bits
+        bits             bit count for bit-fields, otherwise None
         pointer
         constness
         reference
@@ -178,7 +178,7 @@ class ValueType:
 
     type = None
     sign = None
-    bits = 0
+    bits = None
     constness = 0
     pointer = 0
     typeScopeId = None
@@ -188,7 +188,8 @@ class ValueType:
     def __init__(self, element):
         self.type = element.get('valueType-type')
         self.sign = element.get('valueType-sign')
-        self.bits = int(element.get('valueType-bits', 0))
+        self.bits = element.get('valueType-bits', None)
+        self.bits = int(self.bits) if self.bits else None
         self.pointer = int(element.get('valueType-pointer', 0))
         self.constness = int(element.get('valueType-constness', 0))
         self.reference = element.get('valueType-reference')
diff --git a/addons/misra.py b/addons/misra.py
index 1bb190adeef..655b5b0c8c5 100755
--- a/addons/misra.py
+++ b/addons/misra.py
@@ -2017,7 +2017,7 @@ def misra_6_1(self, data):
         for token in data.tokenlist:
             if not token.valueType:
                 continue
-            if token.valueType.bits == 0:
+            if token.valueType.bits is None:
                 continue
             if not token.variable:
                 continue
diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index d007b858e15..982bef2a4b2 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -8110,7 +8110,7 @@ std::string ValueType::dump() const
         break;
     }
 
-    if (bits > 0) {
+    if (bits >= 0) {
         ret += " valueType-bits=\"";
         ret += std::to_string(bits);
         ret += '\"';
diff --git a/lib/symboldatabase.h b/lib/symboldatabase.h
index 6d16fddbe84..b260bf08354 100644
--- a/lib/symboldatabase.h
+++ b/lib/symboldatabase.h
@@ -1236,7 +1236,7 @@ class CPPCHECKLIB ValueType {
         DOUBLE,
         LONGDOUBLE
     } type = UNKNOWN_TYPE;
-    nonneg int bits{};                         ///< bitfield bitcount
+    int bits{};                                ///< bitfield bitcount
     nonneg int pointer{};                      ///< 0=>not pointer, 1=>*, 2=>**, 3=>***, etc
     nonneg int constness{};                    ///< bit 0=data, bit 1=*, bit 2=**
     nonneg int volatileness{};                 ///< bit 0=data, bit 1=*, bit 2=**
diff --git a/lib/token.h b/lib/token.h
index bf6d0bc0f7d..494bfaa01cb 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -82,7 +82,7 @@ struct TokenImpl {
     nonneg int mIndex{};
 
     /** Bitfield bit count. */
-    unsigned char mBits{};
+    char mBits = -1;
 
     // AST..
     Token* mAstOperand1{};
@@ -751,9 +751,9 @@ class CPPCHECKLIB Token {
 
     // cppcheck-suppress unusedFunction
     bool isBitfield() const {
-        return mImpl->mBits > 0;
+        return mImpl->mBits >= 0;
     }
-    unsigned char bits() const {
+    char bits() const {
         return mImpl->mBits;
     }
     const std::set<TemplateSimplifier::TokenAndName*>* templateSimplifierPointers() const {
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 83f2c660baf..f1c4993ebbd 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -10015,7 +10015,7 @@ void Tokenizer::simplifyBitfields()
             !Token::simpleMatch(tok->tokAt(2), "default :")) {
             Token *tok1 = typeTok->next();
             if (Token::Match(tok1, "%name% : %num% [;=]"))
-                tok1->setBits(static_cast<unsigned char>(MathLib::toBigNumber(tok1->tokAt(2))));
+                tok1->setBits(static_cast<char>(MathLib::toBigNumber(tok1->tokAt(2))));
             if (tok1 && tok1->tokAt(2) &&
                 (Token::Match(tok1->tokAt(2), "%bool%|%num%") ||
                  !Token::Match(tok1->tokAt(2), "public|protected|private| %type% ::|<|,|{|;"))) {
@@ -10041,9 +10041,9 @@ void Tokenizer::simplifyBitfields()
             Token *newTok = typeTok->insertToken(name);
             newTok->isAnonymousBitfield(true);
             if (newTok->tokAt(2)->isBoolean())
-                newTok->setBits(static_cast<unsigned char>(newTok->strAt(2) == "true"));
+                newTok->setBits(static_cast<char>(newTok->strAt(2) == "true"));
             else
-                newTok->setBits(static_cast<unsigned char>(MathLib::toBigNumber(newTok->tokAt(2))));
+                newTok->setBits(static_cast<char>(MathLib::toBigNumber(newTok->tokAt(2))));
             newTok->deleteNext(2);
         }
 
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 81e65c8347f..a102082a82b 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -440,7 +440,7 @@ static Result accumulateStructMembers(const Scope* scope, F f, ValueFlow::Accura
     for (const Variable& var : scope->varlist) {
         if (var.isStatic())
             continue;
-        const size_t bits = var.nameToken() ? var.nameToken()->bits() : 0;
+        const char bits = var.nameToken() ? var.nameToken()->bits() : -1;
         if (const ValueType* vt = var.valueType()) {
             if (vt->type == ValueType::Type::RECORD && vt->typeScope == scope)
                 return {0, false};
@@ -455,7 +455,7 @@ static Result accumulateStructMembers(const Scope* scope, F f, ValueFlow::Accura
             else
                 total = f(total, *vt, dim, bits);
         }
-        if (accuracy == ValueFlow::Accuracy::ExactOrZero && total == 0 && bits == 0)
+        if (accuracy == ValueFlow::Accuracy::ExactOrZero && total == 0 && bits == -1)
             return {0, false};
     }
     return {total, true};
@@ -537,10 +537,17 @@ size_t ValueFlow::getSizeOf(const ValueType &vt, const Settings &settings, Accur
     if (vt.type == ValueType::Type::RECORD && vt.typeScope) {
         size_t currentBitCount = 0;
         size_t currentBitfieldAlloc = 0;
-        auto accHelper = [&](size_t total, const ValueType& vt2, size_t dim, size_t bits) -> size_t {
+        auto accHelper = [&](size_t total, const ValueType& vt2, size_t dim, char bits) -> size_t {
             const size_t charBit = settings.platform.char_bit;
             size_t n = ValueFlow::getSizeOf(vt2, settings,accuracy, ++maxRecursion);
             size_t a = getAlignOf(vt2, settings, accuracy);
+            if (bits == 0) {
+                if (currentBitfieldAlloc == 0) {
+                    bits = n * charBit;
+                } else {
+                    bits = currentBitfieldAlloc * charBit - currentBitCount;
+                }
+            }
             if (bits > 0) {
                 size_t ret = total;
                 if (currentBitfieldAlloc == 0) {

From b59140b511bedd7d099ef39c1b542e623a85d2fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Tue, 24 Jun 2025 14:09:53 +0200
Subject: [PATCH 07/15] add test for bit-field with greater number of bits than
 its type

---
 test/testvalueflow.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 1d00d0b8133..d8908294a9b 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -9131,6 +9131,9 @@ class TestValueFlow : public TestFixture {
                       "unsigned int   : 0;\n"
                       "unsigned int b : 16;\n",
                       8);
+
+        testBitfields("unsigned char a : 16;\n",
+                      2);
     }
 };
 

From bfd9490e7f83b8e647203d5ec87b4ac1979263d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Tue, 24 Jun 2025 14:09:34 +0200
Subject: [PATCH 08/15] account for bit-fields with greater number of bits than
 its type

---
 lib/token.h       | 6 +++---
 lib/tokenize.cpp  | 6 +++---
 lib/valueflow.cpp | 8 ++++++--
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/token.h b/lib/token.h
index 494bfaa01cb..b722609cb62 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -82,7 +82,7 @@ struct TokenImpl {
     nonneg int mIndex{};
 
     /** Bitfield bit count. */
-    char mBits = -1;
+    MathLib::bigint mBits = -1;
 
     // AST..
     Token* mAstOperand1{};
@@ -753,7 +753,7 @@ class CPPCHECKLIB Token {
     bool isBitfield() const {
         return mImpl->mBits >= 0;
     }
-    char bits() const {
+    MathLib::bigint bits() const {
         return mImpl->mBits;
     }
     const std::set<TemplateSimplifier::TokenAndName*>* templateSimplifierPointers() const {
@@ -767,7 +767,7 @@ class CPPCHECKLIB Token {
             mImpl->mTemplateSimplifierPointers = new std::set<TemplateSimplifier::TokenAndName*>;
         mImpl->mTemplateSimplifierPointers->insert(tokenAndName);
     }
-    void setBits(const unsigned char b) {
+    void setBits(const MathLib::bigint b) {
         mImpl->mBits = b;
     }
 
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index f1c4993ebbd..8bcefa60c97 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -10015,7 +10015,7 @@ void Tokenizer::simplifyBitfields()
             !Token::simpleMatch(tok->tokAt(2), "default :")) {
             Token *tok1 = typeTok->next();
             if (Token::Match(tok1, "%name% : %num% [;=]"))
-                tok1->setBits(static_cast<char>(MathLib::toBigNumber(tok1->tokAt(2))));
+                tok1->setBits(MathLib::toBigNumber(tok1->tokAt(2)));
             if (tok1 && tok1->tokAt(2) &&
                 (Token::Match(tok1->tokAt(2), "%bool%|%num%") ||
                  !Token::Match(tok1->tokAt(2), "public|protected|private| %type% ::|<|,|{|;"))) {
@@ -10041,9 +10041,9 @@ void Tokenizer::simplifyBitfields()
             Token *newTok = typeTok->insertToken(name);
             newTok->isAnonymousBitfield(true);
             if (newTok->tokAt(2)->isBoolean())
-                newTok->setBits(static_cast<char>(newTok->strAt(2) == "true"));
+                newTok->setBits(newTok->strAt(2) == "true");
             else
-                newTok->setBits(static_cast<char>(MathLib::toBigNumber(newTok->tokAt(2))));
+                newTok->setBits(MathLib::toBigNumber(newTok->tokAt(2)));
             newTok->deleteNext(2);
         }
 
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index a102082a82b..0de180e9d3f 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -440,7 +440,7 @@ static Result accumulateStructMembers(const Scope* scope, F f, ValueFlow::Accura
     for (const Variable& var : scope->varlist) {
         if (var.isStatic())
             continue;
-        const char bits = var.nameToken() ? var.nameToken()->bits() : -1;
+        const MathLib::bigint bits = var.nameToken() ? var.nameToken()->bits() : -1;
         if (const ValueType* vt = var.valueType()) {
             if (vt->type == ValueType::Type::RECORD && vt->typeScope == scope)
                 return {0, false};
@@ -537,7 +537,7 @@ size_t ValueFlow::getSizeOf(const ValueType &vt, const Settings &settings, Accur
     if (vt.type == ValueType::Type::RECORD && vt.typeScope) {
         size_t currentBitCount = 0;
         size_t currentBitfieldAlloc = 0;
-        auto accHelper = [&](size_t total, const ValueType& vt2, size_t dim, char bits) -> size_t {
+        auto accHelper = [&](size_t total, const ValueType& vt2, size_t dim, MathLib::bigint bits) -> size_t {
             const size_t charBit = settings.platform.char_bit;
             size_t n = ValueFlow::getSizeOf(vt2, settings,accuracy, ++maxRecursion);
             size_t a = getAlignOf(vt2, settings, accuracy);
@@ -558,6 +558,10 @@ size_t ValueFlow::getSizeOf(const ValueType &vt, const Settings &settings, Accur
                     currentBitfieldAlloc = n;
                     currentBitCount = 0;
                 }
+                while (bits > charBit * currentBitfieldAlloc) {
+                    ret += currentBitfieldAlloc;
+                    bits -= charBit * currentBitfieldAlloc;
+                }
                 currentBitCount += bits;
                 return ret;
             }

From 93eb7720c35204a822066ed2294bcff479df9c96 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Tue, 24 Jun 2025 15:11:36 +0200
Subject: [PATCH 09/15] change string of token inserted for unnamed bit-fields

---
 lib/checkclass.cpp     |  2 +-
 lib/checkunusedvar.cpp |  2 +-
 lib/token.h            | 10 +++++-----
 lib/tokenize.cpp       |  4 ++--
 test/testtokenize.cpp  | 12 ++++++------
 5 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/lib/checkclass.cpp b/lib/checkclass.cpp
index 83bcc8b8e06..c1171345676 100644
--- a/lib/checkclass.cpp
+++ b/lib/checkclass.cpp
@@ -231,7 +231,7 @@ void CheckClass::constructors()
                 if (usage.assign || usage.init || var.isStatic())
                     continue;
 
-                if (var.nameToken() && var.nameToken()->isAnonymousBitfield())
+                if (var.nameToken() && var.nameToken()->isAnonymous())
                     continue;
 
                 if (var.valueType() && var.valueType()->pointer == 0 && var.type() && var.type()->needInitialization == Type::NeedInitialization::False && var.type()->derivedFrom.empty())
diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 687f5c5983b..49602a28f25 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1575,7 +1575,7 @@ void CheckUnusedVar::checkStructMemberUsage()
             if (isInherited && !var.isPrivate())
                 continue;
 
-            if (var.nameToken() && (var.nameToken()->isAttributeUnused() || var.nameToken()->isAnonymousBitfield()))
+            if (var.nameToken() && (var.nameToken()->isAttributeUnused() || var.nameToken()->isAnonymous()))
                 continue;
 
             if (mTokenizer->isVarUsedInTemplate(var.declarationId()))
diff --git a/lib/token.h b/lib/token.h
index b722609cb62..01aab826628 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -742,11 +742,11 @@ class CPPCHECKLIB Token {
         setFlag(fIsInitBracket, b);
     }
 
-    bool isAnonymousBitfield() const {
-        return getFlag(fIsAnonymousBitfield);
+    bool isAnonymous() const {
+        return getFlag(fIsAnonymous);
     }
-    void isAnonymousBitfield(bool b) {
-        setFlag(fIsAnonymousBitfield, b);
+    void isAnonymous(bool b) {
+        setFlag(fIsAnonymous, b);
     }
 
     // cppcheck-suppress unusedFunction
@@ -1433,7 +1433,7 @@ class CPPCHECKLIB Token {
         fIsFinalType            = (1ULL << 42), // Is this a type with final specifier
         fIsInitComma            = (1ULL << 43), // Is this comma located inside some {..}. i.e: {1,2,3,4}
         fIsInitBracket          = (1ULL << 44), // Is this bracket used as a part of variable initialization i.e: int a{5}, b(2);
-        fIsAnonymousBitfield    = (1ULL << 45), // Is this a token added for an unnamed bit-field
+        fIsAnonymous            = (1ULL << 45), // Is this a token added for an unnamed bit-field
     };
 
     enum : std::uint8_t {
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 8bcefa60c97..775e52b7493 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -10037,9 +10037,9 @@ void Tokenizer::simplifyBitfields()
         } else if (Token::Match(typeTok, "%type% : %num%|%bool% ;") &&
                    typeTok->str() != "default") {
             const std::size_t id = anonymousBitfieldCounter++;
-            const std::string name = "__cppcheck_anon_bit_field_" + std::to_string(id) + "__";
+            const std::string name = "anonymous@" + std::to_string(id);
             Token *newTok = typeTok->insertToken(name);
-            newTok->isAnonymousBitfield(true);
+            newTok->isAnonymous(true);
             if (newTok->tokAt(2)->isBoolean())
                 newTok->setBits(newTok->strAt(2) == "true");
             else
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index f0659efe6ea..d204c51eb59 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -4724,7 +4724,7 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS("struct RGB { unsigned int r ; unsigned int g ; unsigned int b ; } ;", tokenizeAndStringify(code1));
 
         const char code2[] = "struct A { int a : 3; int : 3; int c : 3; };";
-        ASSERT_EQUALS("struct A { int a ; int __cppcheck_anon_bit_field_0__ ; int c ; } ;", tokenizeAndStringify(code2));
+        ASSERT_EQUALS("struct A { int a ; int anonymous@0 ; int c ; } ;", tokenizeAndStringify(code2));
 
         const char code3[] = "struct A { virtual void f() {} int f1 : 1; };";
         ASSERT_EQUALS("struct A { virtual void f ( ) { } int f1 ; } ;", tokenizeAndStringify(code3));
@@ -4738,7 +4738,7 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS("struct A { bool b ; bool c ; } ;", tokenizeAndStringify(code2));
 
         const char code3[] = "struct A { bool : true; };";
-        ASSERT_EQUALS("struct A { bool __cppcheck_anon_bit_field_0__ ; } ;", tokenizeAndStringify(code3));
+        ASSERT_EQUALS("struct A { bool anonymous@0 ; } ;", tokenizeAndStringify(code3));
     }
 
     void bitfields7() { // ticket #1987
@@ -4789,7 +4789,7 @@ class TestTokenizer : public TestFixture {
 
     void bitfields12() { // ticket #3485 (segmentation fault)
         const char code[] = "{a:1;};\n";
-        ASSERT_EQUALS("{ a __cppcheck_anon_bit_field_0__ ; } ;", tokenizeAndStringify(code));
+        ASSERT_EQUALS("{ a anonymous@0 ; } ;", tokenizeAndStringify(code));
     }
 
     void bitfields13() { // ticket #3502 (segmentation fault)
@@ -4829,9 +4829,9 @@ class TestTokenizer : public TestFixture {
                             "};\n";
         const char expected[] = "struct S {\n"
                                 "volatile uint32_t a ;\n"
-                                "volatile uint32_t __cppcheck_anon_bit_field_0__ ;\n"
+                                "volatile uint32_t anonymous@0 ;\n"
                                 "volatile uint32_t b ;\n"
-                                "volatile uint32_t __cppcheck_anon_bit_field_1__ ;\n"
+                                "volatile uint32_t anonymous@1 ;\n"
                                 "} ;";
         ASSERT_EQUALS(expected, tokenizeAndStringify(code));
 
@@ -4841,7 +4841,7 @@ class TestTokenizer : public TestFixture {
                              "};\n";
         const char expected2[] = "struct S {\n"
                                  "const volatile uint32_t a ;\n"
-                                 "const volatile uint32_t __cppcheck_anon_bit_field_0__ ;\n"
+                                 "const volatile uint32_t anonymous@0 ;\n"
                                  "} ;";
         ASSERT_EQUALS(expected2, tokenizeAndStringify(code2));
     }

From de24a8f9ee9bb030b2ccbbaa0beec6284ade06ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Wed, 25 Jun 2025 09:05:58 +0200
Subject: [PATCH 10/15] update comment

---
 lib/token.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/token.h b/lib/token.h
index 01aab826628..5c6b2295d4b 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -1433,7 +1433,7 @@ class CPPCHECKLIB Token {
         fIsFinalType            = (1ULL << 42), // Is this a type with final specifier
         fIsInitComma            = (1ULL << 43), // Is this comma located inside some {..}. i.e: {1,2,3,4}
         fIsInitBracket          = (1ULL << 44), // Is this bracket used as a part of variable initialization i.e: int a{5}, b(2);
-        fIsAnonymous            = (1ULL << 45), // Is this a token added for an unnamed bit-field
+        fIsAnonymous            = (1ULL << 45), // Is this a token added for an unnamed member
     };
 
     enum : std::uint8_t {

From 60ec8283809a2e24fd4fa02f4063f2c3ddc58c30 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Wed, 25 Jun 2025 09:07:22 +0200
Subject: [PATCH 11/15] skip unnamed variables in checkclass and checkunusedvar

---
 lib/checkclass.cpp     | 2 +-
 lib/checkunusedvar.cpp | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/checkclass.cpp b/lib/checkclass.cpp
index c1171345676..8a12a3e2f66 100644
--- a/lib/checkclass.cpp
+++ b/lib/checkclass.cpp
@@ -231,7 +231,7 @@ void CheckClass::constructors()
                 if (usage.assign || usage.init || var.isStatic())
                     continue;
 
-                if (var.nameToken() && var.nameToken()->isAnonymous())
+                if (!var.nameToken() || var.nameToken()->isAnonymous())
                     continue;
 
                 if (var.valueType() && var.valueType()->pointer == 0 && var.type() && var.type()->needInitialization == Type::NeedInitialization::False && var.type()->derivedFrom.empty())
diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 49602a28f25..a7e26fe41fc 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1575,7 +1575,7 @@ void CheckUnusedVar::checkStructMemberUsage()
             if (isInherited && !var.isPrivate())
                 continue;
 
-            if (var.nameToken() && (var.nameToken()->isAttributeUnused() || var.nameToken()->isAnonymous()))
+            if (!var.nameToken() || var.nameToken()->isAttributeUnused() || var.nameToken()->isAnonymous())
                 continue;
 
             if (mTokenizer->isVarUsedInTemplate(var.declarationId()))

From 373922d97fc944ec70d6d8f96e91ce85a63ee177 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Wed, 25 Jun 2025 11:02:23 +0200
Subject: [PATCH 12/15] add test for too large bit-fields

---
 test/testtokenize.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index d204c51eb59..7107eb091d0 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -304,6 +304,7 @@ class TestTokenizer : public TestFixture {
         TEST_CASE(bitfields15); // ticket #7747 (enum Foo {A,B}:4;)
         TEST_CASE(bitfields16); // Save bitfield bit count
         TEST_CASE(bitfields17);
+        TEST_CASE(bitfields18);
 
         TEST_CASE(simplifyNamespaceStd);
 
@@ -4846,6 +4847,12 @@ class TestTokenizer : public TestFixture {
         ASSERT_EQUALS(expected2, tokenizeAndStringify(code2));
     }
 
+    void bitfields18() {
+        const char code[] = "struct S { unsigned int a : 100000; };";
+        (void) tokenizeAndStringify(code);
+        ASSERT_EQUALS("[test.cpp:1:29]: (warning) Bit-field size exceeds max number of bits 32767 [tooLargeBitField]\n", errout_str());
+    }
+
     void simplifyNamespaceStd() {
         const char *expected;
 

From 480662379e933c904d4db3aea376d718020bd853 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Wed, 25 Jun 2025 10:38:53 +0200
Subject: [PATCH 13/15] use short for bit count, print error on larger values

---
 lib/token.h      | 14 ++++++++++----
 lib/tokenize.cpp | 18 +++++++++++++++---
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/lib/token.h b/lib/token.h
index 5c6b2295d4b..a1f78c30245 100644
--- a/lib/token.h
+++ b/lib/token.h
@@ -82,7 +82,7 @@ struct TokenImpl {
     nonneg int mIndex{};
 
     /** Bitfield bit count. */
-    MathLib::bigint mBits = -1;
+    short mBits = -1;
 
     // AST..
     Token* mAstOperand1{};
@@ -753,7 +753,7 @@ class CPPCHECKLIB Token {
     bool isBitfield() const {
         return mImpl->mBits >= 0;
     }
-    MathLib::bigint bits() const {
+    short bits() const {
         return mImpl->mBits;
     }
     const std::set<TemplateSimplifier::TokenAndName*>* templateSimplifierPointers() const {
@@ -767,8 +767,14 @@ class CPPCHECKLIB Token {
             mImpl->mTemplateSimplifierPointers = new std::set<TemplateSimplifier::TokenAndName*>;
         mImpl->mTemplateSimplifierPointers->insert(tokenAndName);
     }
-    void setBits(const MathLib::bigint b) {
-        mImpl->mBits = b;
+    bool setBits(const MathLib::bigint b) {
+        const MathLib::bigint max = std::numeric_limits<short>::max();
+        if (b > max) {
+            mImpl->mBits = max;
+            return false;
+        }
+        mImpl->mBits = b < 0 ? -1 : b;
+        return true;
     }
 
     bool isUtf8() const {
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 775e52b7493..ae2791738f1 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -10007,6 +10007,14 @@ void Tokenizer::simplifyBitfields()
             }
         }
 
+        const auto tooLargeError = [this](const Token *tok) {
+            const MathLib::bigint max = std::numeric_limits<short>::max();
+            reportError(tok,
+                        Severity::warning,
+                        "tooLargeBitField",
+                        "Bit-field size exceeds max number of bits " + std::to_string(max));
+        };
+
         Token* typeTok = tok->next();
         while (Token::Match(typeTok, "const|volatile"))
             typeTok = typeTok->next();
@@ -10015,7 +10023,8 @@ void Tokenizer::simplifyBitfields()
             !Token::simpleMatch(tok->tokAt(2), "default :")) {
             Token *tok1 = typeTok->next();
             if (Token::Match(tok1, "%name% : %num% [;=]"))
-                tok1->setBits(MathLib::toBigNumber(tok1->tokAt(2)));
+                if (!tok1->setBits(MathLib::toBigNumber(tok1->tokAt(2))))
+                    tooLargeError(tok1->tokAt(2));
             if (tok1 && tok1->tokAt(2) &&
                 (Token::Match(tok1->tokAt(2), "%bool%|%num%") ||
                  !Token::Match(tok1->tokAt(2), "public|protected|private| %type% ::|<|,|{|;"))) {
@@ -10040,10 +10049,13 @@ void Tokenizer::simplifyBitfields()
             const std::string name = "anonymous@" + std::to_string(id);
             Token *newTok = typeTok->insertToken(name);
             newTok->isAnonymous(true);
+            bool failed;
             if (newTok->tokAt(2)->isBoolean())
-                newTok->setBits(newTok->strAt(2) == "true");
+                failed = !newTok->setBits(newTok->strAt(2) == "true");
             else
-                newTok->setBits(MathLib::toBigNumber(newTok->tokAt(2)));
+                failed = !newTok->setBits(MathLib::toBigNumber(newTok->tokAt(2)));
+            if (failed)
+                tooLargeError(newTok->tokAt(2));
             newTok->deleteNext(2);
         }
 

From cc64353a52519cde0604cf6a12241c501ecf10d8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Thu, 26 Jun 2025 09:54:11 +0200
Subject: [PATCH 14/15] force Unix64 platform in bitfields test

---
 test/testvalueflow.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index d8908294a9b..68656d5c356 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -9084,8 +9084,9 @@ class TestValueFlow : public TestFixture {
 
 #define testBitfields(structBody, expectedSize) testBitfields_(__FILE__, __LINE__, structBody, expectedSize)
     void testBitfields_(const char *file, int line, const std::string &structBody, std::size_t expectedSize) {
+        const Settings settingsUnix64 = settingsBuilder().platform(Platform::Type::Unix64).build();
         const std::string code = "struct S { " + structBody + " }; const std::size_t size = sizeof(S);";
-        const auto values = tokenValues(code.c_str(), "( S");
+        const auto values = tokenValues(code.c_str(), "( S", &settingsUnix64);
         ASSERT_LOC(!values.empty(), file, line);
         ASSERT_EQUALS_LOC(expectedSize, values.back().intvalue, file, line);
     }

From 1e455057f2841ecd31b3bef82f58112a04d6b4bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Fri, 4 Jul 2025 11:58:20 +0200
Subject: [PATCH 15/15] add isAnonymous to dumpfile and cppcheckdata

---
 addons/cppcheckdata.py | 6 +++++-
 lib/tokenize.cpp       | 2 ++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/addons/cppcheckdata.py b/addons/cppcheckdata.py
index a4257e2a3ed..b0e53161f3a 100755
--- a/addons/cppcheckdata.py
+++ b/addons/cppcheckdata.py
@@ -263,6 +263,7 @@ class Token:
         isComplex
         isRestrict
         isAttributeExport
+        isAnonymous
         varId              varId for token, each variable has a unique non-zero id
         exprId             exprId for token, each expression has a unique non-zero id
         variable           Variable information for this token. See the Variable class.
@@ -324,6 +325,7 @@ class Token:
     isComplex = False
     isRestrict = False
     isAttributeExport = False
+    isAnonymous = False
     exprId = None
     varId = None
     variableId = None
@@ -407,6 +409,8 @@ def __init__(self, element):
             self.isRestrict = True
         if element.get('isAttributeExport'):
             self.isAttributeExport = True
+        if element.get('isAnonymous'):
+            self.isAnonymous = True
         self.linkId = element.get('link')
         self.link = None
         if element.get('varId'):
@@ -440,7 +444,7 @@ def __repr__(self):
                 "isChar", "isBoolean", "isOp", "isArithmeticalOp", "isAssignmentOp", 
                 "isComparisonOp", "isLogicalOp", "isCast", "externLang", "isExpandedMacro", 
                 "isRemovedVoidParameter", "isSplittedVarDeclComma", "isSplittedVarDeclEq", 
-                "isImplicitInt", "isComplex", "isRestrict", "isAttributeExport", "linkId", 
+                "isImplicitInt", "isComplex", "isRestrict", "isAttributeExport", "isAnonymous", "linkId",
                 "varId", "variableId", "functionId", "valuesId", "valueType",
                 "typeScopeId", "astParentId", "astOperand1Id", "file",
                 "linenr", "column"]
diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index ae2791738f1..7be8b213504 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -6103,6 +6103,8 @@ void Tokenizer::dump(std::ostream &out) const
             outs += " isAttributeFallthrough=\"true\"";
         if (tok->isInitBracket())
             outs += " isInitBracket=\"true\"";
+        if (tok->isAnonymous())
+            outs += " isAnonymous=\"true\"";
         if (tok->hasAttributeAlignas()) {
             const std::vector<std::string>& a = tok->getAttributeAlignas();
             outs += " alignas=\"" + ErrorLogger::toxml(a[0]) + "\"";