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Fix #14533, #14536 FN stlcstrConcat, stlcstrAssignment, stlcstrConstructor #8261

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Merged
chrchr-github merged 16 commits into from
Mar 11, 2026
Merged

Fix #14533, #14536 FN stlcstrConcat, stlcstrAssignment, stlcstrConstructor #8261

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5f7d92b
Update checkstl.cpp
chrchr-github Feb 25, 2026
0ec9223
Update teststl.cpp
chrchr-github Feb 25, 2026
d4269dd
Update checkstl.cpp
chrchr-github Feb 25, 2026
4614417
Fix #14536 FN stlcstrConcat with function returning string
web-flow Feb 25, 2026
a8bdf5f
Check operand
web-flow Feb 25, 2026
6559527
Update checkstl.cpp
chrchr-github Feb 26, 2026
1eafc89
Update teststl.cpp
chrchr-github Feb 26, 2026
82b2a0f
Update teststl.cpp
chrchr-github Feb 26, 2026
f6b00d6
Update librarydialog.cpp
chrchr-github Feb 26, 2026
c359ded
Update teststl.cpp
chrchr-github Feb 27, 2026
ed47749
isBinaryOp()
web-flow Feb 28, 2026
a271422
Restrict to STL types
web-flow Mar 2, 2026
995627c
Update checkstl.cpp
chrchr-github Mar 5, 2026
0acf8bd
Update checkstl.cpp
chrchr-github Mar 5, 2026
f282ea2
Merge branch 'danmar:main' into chr_14533
chrchr-github Mar 10, 2026
c34272c
Update checkstl.cpp
chrchr-github Mar 10, 2026
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33 changes: 30 additions & 3 deletions lib/checkstl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1959,6 +1959,35 @@ static bool isLocal(const Token *tok)
return var && !var->isStatic() && var->isLocal();
}

static bool isc_strConcat(const Token* tok)
{
if (!Token::simpleMatch(tok, "+"))
return false;
const Token* cstr = nullptr;
for (const Token* op : { tok->astOperand1(), tok->astOperand2() }) {
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@chrchr-github chrchr-github Mar 10, 2026

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Upstream issue: llvm/llvm-project#185593

if (!Token::simpleMatch(op, "("))
continue;
const Token* dot = op->astOperand1();
if (!Token::simpleMatch(dot, "."))
continue;
if (!Token::Match(dot->astOperand1(), "%var%")) // TODO: function returning string
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continue;
const Variable* var = dot->astOperand1()->variable();
if (!var || !var->isStlStringType())
continue;
if (!Token::Match(dot->astOperand2(), "c_str|data ( )"))
continue;
cstr = op;
break;
}
if (!cstr)
return false;
const Token* strTok = (cstr == tok->astOperand1()) ? tok->astOperand2() : tok->astOperand1();
if (strTok->variable() && strTok->variable()->isStlStringType())
return true;
return strTok->valueType() && strTok->valueType()->container && strTok->valueType()->container->stdStringLike;
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}

namespace {
const std::set<std::string> stl_string_stream = {
"istringstream", "ostringstream", "stringstream", "wstringstream"
Expand Down Expand Up @@ -2072,9 +2101,7 @@ void CheckStl::string_c_str()
tok->variable() && (tok->variable()->isStlStringType() || tok->variable()->isStlStringViewType()) &&
tok->tokAt(2)->variable() && tok->tokAt(2)->variable()->isStlStringType()) {
string_c_strConstructor(tok, tok->variable()->getTypeName());
} else if (printPerformance && tok->next() && tok->next()->variable() && tok->next()->variable()->isStlStringType() && tok->valueType() && tok->valueType()->type == ValueType::CONTAINER &&
((Token::Match(tok->previous(), "%var% + %var% . c_str|data ( )") && tok->previous()->variable() && tok->previous()->variable()->isStlStringType()) ||
(Token::Match(tok->tokAt(-5), "%var% . c_str|data ( ) + %var%") && tok->tokAt(-5)->variable() && tok->tokAt(-5)->variable()->isStlStringType()))) {
} else if (printPerformance && isc_strConcat(tok)) {
string_c_strConcat(tok);
} else if (printPerformance && Token::simpleMatch(tok, "<<") && tok->astOperand2() && Token::Match(tok->astOperand2()->astOperand1(), ". c_str|data ( )")) {
const Token* str = tok->astOperand2()->astOperand1()->astOperand1();
Expand Down
16 changes: 16 additions & 0 deletions test/teststl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4680,6 +4680,22 @@ class TestStl : public TestFixture {
" return s->x.c_str();\n"
"}\n");
ASSERT_EQUALS("", errout_str());

check("std::string f(const std::string& s) {\n" // #14533
" auto x = std::string(\"abc\") + s.c_str();\n"
" auto y = s.c_str() + std::string(\"def\");\n"
" return x + y;\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2:33]: (performance) Concatenating the result of c_str() and a std::string is slow and redundant. [stlcstrConcat]\n"
"[test.cpp:3:24]: (performance) Concatenating the result of c_str() and a std::string is slow and redundant. [stlcstrConcat]\n",
errout_str());

check("std::string get();\n"
"std::string f(const std::string& s) {\n"
" return get() + s.c_str();\n"
"}\n");
ASSERT_EQUALS("[test.cpp:3:18]: (performance) Concatenating the result of c_str() and a std::string is slow and redundant. [stlcstrConcat]\n",
errout_str());
}

void uselessCalls() {
Expand Down
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