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Fix #726 (#if: ?: treats a zero condition as true unless it is written exactly as 0) #728

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Merged
danmar merged 1 commit into from
Nov 7, 2026
Merged

Fix #726 (#if: ?: treats a zero condition as true unless it is written exactly as 0) #728

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4 changes: 2 additions & 2 deletions simplecpp.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1305,7 +1305,7 @@ void simplecpp::TokenList::constFoldUnaryNotPosNeg(simplecpp::Token *tok)
tok->setstr(tok->next->str());
deleteToken(tok->next);
} else if (tok->op == '!' && tok->next && tok->next->number) {
tok->setstr(tok->next->str() == "0" ? "1" : "0");
tok->setstr(stringToLL(tok->next->str()) == 0 ? "1" : "0");
deleteToken(tok->next);
} else if (tok->op == '~' && tok->next && tok->next->number) {
tok->setstr(toString(~stringToLL(tok->next->str())));
Expand Down Expand Up @@ -1571,7 +1571,7 @@ void simplecpp::TokenList::constFoldQuestionOp(Token *&tok1)
deleteToken(trueTok);
deleteToken(falseTok);
} else {
Token * const result = (condTok->str() != "0" ? trueTok : falseTok);
Token * const result = (stringToLL(condTok->str()) != 0 ? trueTok : falseTok);
if (condTok == tok1)
tok1 = result;
deleteToken(condTok->next); // ?
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27 changes: 27 additions & 0 deletions test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2887,6 +2887,32 @@ static void ifShortCircuit()
ASSERT_EQUALS("file0,1,syntax_error,failed to evaluate #if condition, division/modulo by zero\n", toString(outputList));
}

static void ifZeroCondition()
{
// a zero value that is not written as 0 is false
const char * const exprs[] = {
"00 ? 1 : 0",
"-0 ? 1 : 0",
"-X ? 1 : 0",
"0L ? 1 : 0",
"!00 ? 0 : 1",
"!0L ? 0 : 1"
};
for (const char * const expr : exprs) {
const std::string code = std::string("#if ") + expr + "\n"
"1\n"
"#else\n"
"2\n"
"#endif\n";
ASSERT_EQUALS("\n\n\n2", preprocess(code.c_str()));
}

// the selected operand is evaluated
simplecpp::OutputList outputList;
ASSERT_EQUALS("", preprocess("#if 00 ? 1 : 1/0\n#endif\n", &outputList));
ASSERT_EQUALS("file0,1,syntax_error,failed to evaluate #if condition, division/modulo by zero\n", toString(outputList));
}

static void ifTrueFalse()
{
const char code[] = "#if true && !false\n"
Expand Down Expand Up @@ -5123,6 +5149,7 @@ static void runTests(int argc, char **argv, Input input)
TEST_CASE(ifoverflow);
TEST_CASE(ifdiv0);
TEST_CASE(ifShortCircuit);
TEST_CASE(ifZeroCondition);
TEST_CASE(ifTrueFalse);
TEST_CASE(ifalt); // using "and", "or", etc
TEST_CASE(ifexpr);
Expand Down
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