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Fix #709 Do not evaluate #elif after a taken group #710

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Merged
danmar merged 1 commit into from
Nov 4, 2026
Merged

Fix #709 Do not evaluate #elif after a taken group #710

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7 changes: 5 additions & 2 deletions simplecpp.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3839,9 +3839,12 @@ void simplecpp::preprocess(simplecpp::TokenList &output, const simplecpp::TokenL
return;
}

const bool isElif = (rawtok->str() == ELIF || rawtok->str() == ELIFDEF || rawtok->str() == ELIFNDEF);

bool conditionIsTrue;
if (ifstates.top() == AlwaysFalse || (ifstates.top() == ElseIsTrue && rawtok->str() != ELIF &&
rawtok->str() != ELIFDEF && rawtok->str() != ELIFNDEF)) {
// An #if is only evaluated in an active group. An #elif is only evaluated
// if no previous group was taken; otherwise it is skipped (C 6.10.1p6).
if (isElif ? (ifstates.top() != ElseIsTrue) : (ifstates.top() != True)) {
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conditionIsTrue = false;
}
else if (rawtok->str() == IFDEF || rawtok->str() == ELIFDEF) {
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10 changes: 10 additions & 0 deletions test.cpp
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Expand Up @@ -2490,6 +2490,16 @@ static void elif()
"3\n"
"#endif";
ASSERT_EQUALS("\n\n\n\n\n3", preprocess(code3));

// #elif after a taken group must not be evaluated
const char code4[] = "#if 1\n"
"1\n"
"#elif 1/0\n"
"2\n"
"#elif garbage(\n"
"3\n"
"#endif";
ASSERT_EQUALS("\n1", preprocess(code4));
}

static void elifdef()
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