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Fix #14371: FP redundantAssignment for nested union members #8748

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Fix #14371: FP redundantAssignment for nested union members #8748

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d5f2fb4
Fix #14371: FP redundantAssignment for nested union members
DanTheMan2000 Jul 23, 2026
4304c1a
Consolidate union tests into a single test case
DanTheMan2000 Jul 23, 2026
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6 changes: 5 additions & 1 deletion lib/checkother.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -700,8 +700,12 @@ void CheckOtherImpl::checkRedundantAssignment()
// Get next assignment..
const Token *nextAssign = fwdAnalysis.reassign(tokenToCheck, start, scope->bodyEnd);
// extra check for union
if (nextAssign && tokenToCheck != tok->astOperand1())
if (nextAssign && tokenToCheck != tok->astOperand1()) {
nextAssign = fwdAnalysis.reassign(tok->astOperand1(), start, scope->bodyEnd);
// reading another member of the same union in the rhs is a use through aliasing
if (nextAssign && fwdAnalysis.hasOperand(nextAssign->astOperand2(), tokenToCheck))
nextAssign = nullptr;
}

if (!nextAssign)
continue;
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42 changes: 42 additions & 0 deletions test/testother.cpp
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Expand Up @@ -11063,6 +11063,48 @@ class TestOther : public TestFixture {
" Dst.s->y = Src.s->y;\n"
"}\n");
ASSERT_EQUALS("", errout_str());

// Ticket #14371 "redundantAssignment when using a union"
check("union U {\n"
" struct {\n"
" unsigned int abcd;\n"
" } u32;\n"
" struct {\n"
" unsigned short ab;\n"
" unsigned short cd;\n"
" } u16;\n"
"};\n"
"void f1() {\n"
" U m;\n"
" m.u32.abcd = 1234;\n"
" m.u32.abcd = 5 * m.u16.ab;\n"
"}\n"
"void f2(unsigned int a, unsigned short b) {\n"
" U m;\n"
" m.u32.abcd = a;\n"
" m.u32.abcd += 0x8000;\n"
" m.u32.abcd = m.u16.ab * b;\n"
"}\n"
"void f3(unsigned int seed) {\n"
" U m, other;\n"
" other.u32.abcd = seed;\n"
" m.u32.abcd = 1234;\n"
" m.u32.abcd = other.u16.ab * 2;\n"
"}\n"
"void f4(unsigned short x) {\n"
" U m;\n"
" m.u16.ab = x;\n"
" m.u16.cd = 0;\n"
" m.u16.ab = m.u32.abcd / 53;\n"
"}\n"
"void f5(unsigned short x, unsigned int y) {\n"
" U m;\n"
" m.u16.ab = x;\n"
" m.u16.cd = 0;\n"
" m.u16.ab = y;\n"
"}\n", dinit(CheckOptions, $.inconclusive = false));
ASSERT_EQUALS("[test.cpp:24:16] -> [test.cpp:25:16]: (style) Variable 'm.u32.abcd' is reassigned a value before the old one has been used. [redundantAssignment]\n"
"[test.cpp:35:14] -> [test.cpp:37:14]: (style) Variable 'm.u16.ab' is reassigned a value before the old one has been used. [redundantAssignment]\n", errout_str());
}

void redundantVarAssignment_7133() {
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