Fix #12932 FP: uninitvar (use iterators of std::array of size 0) (#6602)

Author: chrchr-github

lib/checkuninitvar.cpp

@@ -1641,6 +1641,11 @@ void CheckUninitVar::valueFlowUninit()
                     const bool isarray = tok->variable()->isArray();
                     if (isarray && tok->variable()->isMember())
                         continue; // Todo: this is a bailout
+                    if (isarray && tok->variable()->isStlType() && Token::simpleMatch(tok->astParent(), ".")) {
+                        const auto yield = astContainerYield(tok);
+                        if (yield != Library::Container::Yield::AT_INDEX && yield != Library::Container::Yield::ITEM)
+                            continue;
+                    }
                     const bool deref = CheckNullPointer::isPointerDeRef(tok, unknown, *mSettings);
                     uninitderef = deref && v->indirect == 0;
                     const bool isleaf = isLeafDot(tok) || uninitderef;

test/testuninitvar.cpp

@@ -6542,6 +6542,17 @@ class TestUninitVar : public TestFixture {
                       "[test.cpp:12]: (error) Uninitialized variable: b\n"
                       "[test.cpp:16]: (error) Uninitialized variable: a\n",
                       errout_str());
+
+        valueFlowUninit("void f() {\n" // # 12932
+                        "    std::array<int, 0> a;\n"
+                        "    if (a.begin() == a.end()) {}\n"
+                        "    std::array<int, 1> b;\n"
+                        "    auto it = b.begin();\n"
+                        "    *it = 0;\n"
+                        "    std::array<int, 1> c;\n"
+                        "    return c.front();\n"
+                        "}\n");
+        ASSERT_EQUALS("[test.cpp:8]: (error) Uninitialized variable: c\n", errout_str());
     }
 
     void valueFlowUninitBreak() { // Do not show duplicate warnings about the same uninitialized value