Does it make sense to use _attribute__ ((nothrow)) inside extern C?

Question

I have some C code being called from C++.
The header resembles the following:

#ifndef CLibH
#define CLibH

#ifdef __cplusplus
extern "C" {
#endif

//C API
void foo(void);
// ...

#ifdef __cplusplus
}
#endif

#endif

Since I'm already using extern C,
is there any benefit to adding the nothrow compiler attribute?

#ifndef CLibH
#define CLibH

#ifdef __cplusplus
extern "C" {
#endif

//C API
void foo(void) __attribute__((nothrow));
// ...

#ifdef __cplusplus
}
#endif

#endif

Does extern C make this redundant?
Are there still advantages to applying it under these circumstances?

@iharob: It could call into external Fortran code, which could throw. — Kerrek SB
– Kerrek SB, Commented Aug 31, 2016 at 18:29
@iharob Exactly. So the compiler should optimize just the same with or without the attribute? I wasn't sure if there were some subtleties with libraries, or if C code could call back into C++, etc. — Trevor Hickey
– Trevor Hickey, Commented Aug 31, 2016 at 18:29
@KerrekSB So "extern C" does not guarantee "no throw". A function can still throw if it is wrapped in "extern C". That makes sense. — Trevor Hickey
– Trevor Hickey, Commented Aug 31, 2016 at 18:31
extern "C" can call straight into C++ code marked as extern "C". So the questions becomes can exceptions propagate out of a C++ function marked as extern "C"? — Richard Critten
– Richard Critten, Commented Aug 31, 2016 at 18:43
I feel very stupid. I myself wrote a c++ plugin system which of course used c to construct classes. Contructors can throw and I used new of course, so it's not redundant at ll. In fact you can externalize any c++ function and use stl, the new operator (which does throw exceptions). The only thing extern "C" does is prevent name mangling. — Iharob Al Asimi
– Iharob Al Asimi, Commented Aug 31, 2016 at 19:17

ivaigult · Accepted Answer · 2016-08-31 18:46:16Z

0

Yes, it does. From gcc documentation:

For example, most functions in the standard C library can be guaranteed not to throw an exception with the notable exceptions of qsort and bsearch that take function pointer arguments.

answered Aug 31, 2016 at 18:46

ivaigult

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