Fix #12462 (False positive: uninitialized data passed by const address, not used in subfunction) (#6115)

Author: danmar

lib/astutils.cpp

@@ -3282,10 +3282,19 @@ static ExprUsage getFunctionUsage(const Token* tok, int indirect, const Settings
         for (const Variable* arg : args) {
             if (!arg)
                 continue;
-            if (arg->isReference())
-                return ExprUsage::PassedByReference;
-            if (arg->isPointer() && indirect == 1)
-                return ExprUsage::PassedByReference;
+            if (arg->isReference() || (arg->isPointer() && indirect == 1)) {
+                if (!ftok->function()->hasBody())
+                    return ExprUsage::PassedByReference;
+                for (const Token* bodytok = ftok->function()->functionScope->bodyStart; bodytok != ftok->function()->functionScope->bodyEnd; bodytok = bodytok->next()) {
+                    if (bodytok->variable() == arg) {
+                        if (arg->isReference())
+                            return ExprUsage::PassedByReference;
+                        if (Token::Match(bodytok->astParent(), "%comp%|!"))
+                            return ExprUsage::NotUsed;
+                        return ExprUsage::PassedByReference;
+                    }
+                }
+            }
         }
         if (!args.empty() && indirect == 0 && !addressOf)
             return ExprUsage::Used;

test/testuninitvar.cpp

@@ -64,6 +64,7 @@ class TestUninitVar : public TestFixture {
         TEST_CASE(uninitvar2_value);    // value flow
         TEST_CASE(valueFlowUninit2_value);
         TEST_CASE(valueFlowUninit_uninitvar2);
+        TEST_CASE(valueFlowUninit_functioncall);
         TEST_CASE(uninitStructMember);  // struct members
         TEST_CASE(uninitvar2_while);
         TEST_CASE(uninitvar2_4494);      // #4494
@@ -4319,6 +4320,36 @@ class TestUninitVar : public TestFixture {
         ASSERT_EQUALS("", errout.str());
     }
 
+    void valueFlowUninit_functioncall() {
+
+        // #12462 - pointer data is not read
+        valueFlowUninit("struct myst { int a; };\n"
+                        "void bar(const void* p) {}\n"
+                        "void foo() {\n"
+                        "  struct myst item;\n"
+                        "  bar(&item);\n"
+                        "}", "test.c");
+        ASSERT_EQUALS("", errout.str());
+
+        valueFlowUninit("struct myst { int a; };\n"
+                        "void bar(const void* p) { a = (p != 0); }\n"
+                        "void foo() {\n"
+                        "  struct myst item;\n"
+                        "  bar(&item);\n"
+                        "  a = item.a;\n" // <- item.a is not initialized
+                        "}", "test.c");
+        ASSERT_EQUALS("[test.c:6]: (error) Uninitialized variable: item.a\n", errout.str());
+
+        valueFlowUninit("struct myst { int a; };\n"
+                        "void bar(struct myst* p) { p->a = 0; }\n"
+                        "void foo() {\n"
+                        "  struct myst item;\n"
+                        "  bar(&item);\n"
+                        "  a = item.a;\n"
+                        "}", "test.c");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void uninitStructMember() { // struct members
         checkUninitVar("struct AB { int a; int b; };\n"
                        "void f(void) {\n"