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Fix #724 (##: valid token pastes are rejected) #725

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Merged
danmar merged 2 commits into from
Nov 6, 2026
Merged

Fix #724 (##: valid token pastes are rejected) #725

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42bb479
Fix #724 (##: valid token pastes are rejected)
dmcppcheck Nov 6, 2026
f2d2413
Update integration test for new ## error message
dmcppcheck Nov 6, 2026
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2 changes: 1 addition & 1 deletion integration_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -501,7 +501,7 @@ def test_define(record_property, tmpdir): # #589
record_property("stderr", stderr)

assert exitcode == 0
assert stderr == "test.cpp:1: syntax error: failed to expand 'TEST_P', Invalid ## usage when expanding 'TEST_P': Unexpected token ')'\n"
assert stderr == "test.cpp:1: syntax error: failed to expand 'TEST_P', Invalid ## usage when expanding 'TEST_P': Combining ')' and '_' yields an invalid token.\n"
assert stdout == '\n'

def test_utf16_bom(tmpdir):
Expand Down
44 changes: 31 additions & 13 deletions simplecpp.cpp
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Expand Up @@ -160,6 +160,25 @@ static bool sameline(const simplecpp::Token *tok1, const simplecpp::Token *tok2)
return tok1 && tok2 && tok1->location.sameline(tok2->location);
}

/** is s a punctuator (C11 6.4.6, C++ [lex.operators]) */
static bool isPunctuator(const std::string &s)
{
static const std::set<std::string> punctuators{
"[", "]", "(", ")", "{", "}", ".", "->", "++", "--", "&", "*", "+", "-", "~", "!",
"/", "%", "<<", ">>", "<", ">", "<=", ">=", "==", "!=", "^", "|", "&&", "||",
"?", ":", ";", "...", "=", "*=", "/=", "%=", "+=", "-=", "<<=", ">>=", "&=", "^=", "|=",
",", "#", "##", "<:", ":>", "<%", "%>", "%:", "%:%:", "::", ".*", "->*", "<=>"
};
return punctuators.find(s) != punctuators.end();
}

/** is s a valid result when a punctuator is pasted with ## */
static bool isValidPunctuatorPaste(const std::string &s)
{
// a pp-number can start with '.'
return isPunctuator(s) || (s.size() >= 2 && s[0] == '.' && std::isdigit(static_cast<unsigned char>(s[1])));
}

static bool isAlternativeBinaryOp(const simplecpp::Token *tok, const std::string &alt)
{
return (tok->name &&
Expand Down Expand Up @@ -2458,17 +2477,17 @@ namespace simplecpp {
if (!sameline(tok, tok->next) || !sameline(tok, tok->next->next))
throw invalidHashHash::unexpectedNewline(tok->location, name());

const bool canBeConcatenatedWithEqual = A->isOneOf("+-*/%&|^") || A->str() == "<<" || A->str() == ">>";
const bool canBeConcatenatedStringOrChar = isStringLiteral(A->str()) || isCharLiteral(A->str());
const bool unexpectedA = (!A->name && !A->number && !A->str().empty() && !canBeConcatenatedWithEqual && !canBeConcatenatedStringOrChar);
// A is a punctuator; the result is checked when B has been expanded
const bool punctuatorA = (!A->name && !A->number && !A->str().empty() && !canBeConcatenatedStringOrChar);

const Token * const B = tok->next->next;
if (!B->name && !B->number && B->op && !B->isOneOf("#="))
throw invalidHashHash::unexpectedToken(tok->location, name(), B);

if ((canBeConcatenatedWithEqual && B->op != '=') ||
(!canBeConcatenatedWithEqual && B->op == '='))
throw invalidHashHash::cannotCombine(tok->location, name(), A, B);
if (!punctuatorA) {
if (!B->name && !B->number && B->op && !B->isOneOf("#="))
throw invalidHashHash::unexpectedToken(tok->location, name(), B);
if (B->op == '=')
throw invalidHashHash::cannotCombine(tok->location, name(), A, B);
}

// Superficial check; more in-depth would in theory be possible _after_ expandArg
if (canBeConcatenatedStringOrChar && (B->number || !B->name))
Expand Down Expand Up @@ -2500,16 +2519,15 @@ namespace simplecpp {
else if (varargs && A->op == ',') {
strAB = ",";
}
else if (varargs && unexpectedA) {
throw invalidHashHash::unexpectedToken(tok->location, name(), A);
}
else {
if (punctuatorA && !isValidPunctuatorPaste(A->str() + tokensB.cfront()->str()))
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throw invalidHashHash::cannotCombine(tok->location, name(), A, tokensB.cfront());
strAB = A->str() + tokensB.cfront()->str();
tokensB.deleteToken(tokensB.front());
}
} else {
if (unexpectedA)
throw invalidHashHash::unexpectedToken(tok->location, name(), A);
if (punctuatorA && !isValidPunctuatorPaste(A->str() + B->str()))
throw invalidHashHash::cannotCombine(tok->location, name(), A, B);
strAB = A->str() + B->str();
}

Expand Down
28 changes: 26 additions & 2 deletions test.cpp
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Expand Up @@ -2134,7 +2134,7 @@ static void hashhash_invalid_1()
const char code[] = "#define f(a) (##x)\nf(1)\n";
simplecpp::OutputList outputList;
ASSERT_EQUALS("", preprocess(code, &outputList));
ASSERT_EQUALS("file0,1,syntax_error,failed to expand 'f', Invalid ## usage when expanding 'f': Unexpected token '('\n", toString(outputList));
ASSERT_EQUALS("file0,1,syntax_error,failed to expand 'f', Invalid ## usage when expanding 'f': Combining '(' and 'x' yields an invalid token.\n", toString(outputList));
}

static void hashhash_invalid_2()
Expand Down Expand Up @@ -2188,14 +2188,36 @@ static void hashhash_empty_va_args()
ASSERT_EQUALS("\n\n\n( 2 )", preprocess(code));
}

static void hashhash_punctuator() // #724
{
const char code[] =
"#define cat(a,b) a##b\n"
"#define MINUS_GT -##>\n"
"#define VA(...) <##__VA_ARGS__\n"
"cat(+,=) cat(<<,=) cat(-,>) cat(&,&) cat(|,|) cat(+,+) cat(<,=) cat(.,5) MINUS_GT VA(<) VA()\n";
simplecpp::OutputList outputList;
ASSERT_EQUALS("\n\n\n+= <<= -> && || ++ <= .5 -> << <", preprocess(code, &outputList));
ASSERT_EQUALS("", toString(outputList));
}

static void hashhash_punctuator_invalid()
{
const char code[] =
"#define cat(a,b) a##b\n"
"cat(+,x)\n";
simplecpp::OutputList outputList;
ASSERT_EQUALS("", preprocess(code, &outputList));
ASSERT_EQUALS("file0,1,syntax_error,failed to expand 'cat', Invalid ## usage when expanding 'cat': Combining '+' and 'x' yields an invalid token.\n", toString(outputList));
}

static void hashhash_va_args_unexpected()
{
const char code[] =
"#define C(...)!##__VA_ARGS__\n"
"C(1)\n";
simplecpp::OutputList outputList;
preprocess(code, simplecpp::DUI(), &outputList);
ASSERT_EQUALS("file0,1,syntax_error,failed to expand 'C', Invalid ## usage when expanding 'C': Unexpected token '!'\n", toString(outputList));
ASSERT_EQUALS("file0,1,syntax_error,failed to expand 'C', Invalid ## usage when expanding 'C': Combining '!' and '1' yields an invalid token.\n", toString(outputList));
}

static void hashhash_universal_character()
Expand Down Expand Up @@ -4942,6 +4964,8 @@ static void runTests(int argc, char **argv, Input input)
TEST_CASE(hashhash_invalid_missing_args);
TEST_CASE(hashhash_null_stmt);
TEST_CASE(hashhash_empty_va_args);
TEST_CASE(hashhash_punctuator);
TEST_CASE(hashhash_punctuator_invalid);
TEST_CASE(hashhash_va_args_unexpected);

// C standard, 5.1.1.2, paragraph 4:
Expand Down
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