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fix #11691: FP throwInNoexceptFunction with if constexpr in template #6962

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fix #11691: FP throwInNoexceptFunction with if constexpr in template #6962

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21 changes: 21 additions & 0 deletions lib/checkexceptionsafety.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
#include "symboldatabase.h"
#include "token.h"

#include <algorithm>
#include <list>
#include <set>
#include <utility>
Expand Down Expand Up @@ -239,6 +240,13 @@ void CheckExceptionSafety::catchExceptionByValueError(const Token *tok)
"as a (const) reference which is usually recommended in C++.", CWE398, Certainty::normal);
}

static bool isPossibleBool(const Token *tok, bool b)
{
const std::list<ValueFlow::Value> &values = tok->values();
return std::any_of(values.cbegin(), values.cend(), [&](const ValueFlow::Value &value) {
return value.isIntValue() && value.isPossible() && value.intvalue == static_cast<int>(b);
});
}

static const Token * functionThrowsRecursive(const Function * function, std::set<const Function *> & recursive)
{
Expand All @@ -251,6 +259,19 @@ static const Token * functionThrowsRecursive(const Function * function, std::set

for (const Token *tok = function->functionScope->bodyStart->next();
tok != function->functionScope->bodyEnd; tok = tok->next()) {
if (Token::simpleMatch(tok, "if")) {
tok = tok->astParent();
const Token *condTok = tok->astOperand2();
// check if condition is possibly false, since template arguments are not set to known
if (isPossibleBool(condTok, false)) {
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Somehow we should check if the possible values are template arguments. You can check Token::templateArg for "possible" operands .

If the condition is false you skip the if-body but if the condition is true you do nothing, you should skip the else body then.

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The utility function I introduce in #7045 would be useful for this, so maybe I should wait for that one.

tok = tok->link()->next();
if (Token::simpleMatch(tok, "{"))
tok = tok->link();
else while (tok && !Token::simpleMatch(tok, ";"))
tok = tok->next();
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this does not seem to be formatted properly. we have the runformat script in the cppcheck folder could you run that..

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Hm, this seems to be what uncrustify wants. But I could add braces to make it more readable.

continue;
}
}
if (Token::simpleMatch(tok, "try {"))
tok = tok->linkAt(1); // skip till start of catch clauses
if (tok->str() == "throw")
Expand Down
21 changes: 21 additions & 0 deletions test/testexceptionsafety.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -361,6 +361,27 @@ class TestExceptionSafety : public TestFixture {
// avoid false positives
check("const char *func() throw() { return 0; }");
ASSERT_EQUALS("", errout_str());


// #11691: FP throwInNoexceptFunction with if constexpr in template
check("template<bool IsNoThrow>\n"
"static void* MyNew(size_t Size) noexcept(IsNoThrow) {\n"
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this test case can be reduced:

template<bool IsNoThrow>
static void foo(size_t Size) noexcept(IsNoThrow) {
    if constexpr (!IsNoThrow) {
        throw std::bad_alloc();
    }
}

foo<true>(123);

" void* Memory = std::malloc(Size);\n"
" if (!Memory) {\n"
" if constexpr (!IsNoThrow) {\n"
" throw std::bad_alloc();\n"
" }\n"
" }\n"
" return Memory;\n"
"}\n"
"void* AllocateMemory(size_t Size, bool UseNoThrow) {\n"
" if (UseNoThrow) {\n"
" return MyNew<true>(Size);\n"
" } else {\n"
" return MyNew<false>(Size);\n"
" }\n"
"}\n");
ASSERT_EQUALS("", errout_str());
}

void unhandledExceptionSpecification1() { // #4800
Expand Down
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