[cfe-dev] is there any way to detect temporary referencing with clang?

[David Blaikie]

Either msan or the static analyzer might catch this, but there's no
straight up compiler warning for this (and as the issue is interprocedural,
any such warning would have to be assisted by source annotations)
On Jul 15, 2014 11:58 PM, "Dennis Luehring" <dl.soluz at gmx.net> wrote:

> or is that already covered by https://code.google.com/p/
> address-sanitizer/issues/detail?id=73
>
> example:
>
> #include <cstdint>
> #include <cstdio>
>
> class user_t
> {
> public:
>   user_t(const int64_t& p_a):
>     m_a(p_a)
>   {
>   }
>
>   const int64_t& m_a; // someone added evil & while refactoring
>
>   int64_t use_it() const
>   {
>     return m_a;
>   }
> };
>
> #define EVIL_TEMPORARY
>
> //example result:
> //EVIL_TEMPORARY  Mode
> //     X          Release  --> a: 8, user_a: 75769734271860736 FAIL
> //     X          Debug    --> a: 8, user_a: 7 FAIL
> //     -          Release  --> a: 8, user_a: 8 OK
> //     -          Debug    --> a: 8, user_a: 8 OK
>
> int main(int argc, char** argv)
> {
>   const int64_t value = argc+6;
>   int64_t a = value;
>
> #if defined(EVIL_TEMPORARY)
>   const user_t user(a++); // the temporary result of a++ is referenced by
> member m_a
> #else
>   const user_t user(a);
>   ++a;
> #endif
>   const int64_t user_a = user.use_it();
>   const bool ok = user_a == a;
>   printf("a: %I64d, user_a: %I64d %s\n", a, user_a, ok ? "OK":"FAIL");
>   return ok;
> }
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>
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