CODEWITHSUNDEEP
cgccoptimizationinlinecompiler-optimization
Djordje Zivanovic
Djordje Zivanovic

Reputation: 304

Gcc compiler optimization function inlining

Does gcc add atribute in signature of function, or not? Will these functions be compiled if it's in the same source file?

void*__attribute__ ((noinline)) GetCurrentIp(void) {
    some code...
}


void*GetCurrentIp(void);
void*__attribute__ ((always_inline)) GetCurrentIp(void)

Upvotes: 0

Views: 272

Answers (2)

Armali
Armali

Reputation: 19395

Even if the question is about C, we can let g++ answer it (see Function Names as Strings).

f.C:

#include <stdio.h>

extern "C"
void *__attribute__((noinline)) GetCurrentIp(void)
{
    printf("signature of %s: %s\n", __func__, __PRETTY_FUNCTION__);
    return __builtin_return_address(0);
}

int main()
{
    GetCurrentIp();
    return 0;
}

> g++ f.C
> a.out
signature of GetCurrentIp: void* GetCurrentIp()

So, the attribute is not part of the signature.

Upvotes: 2

Anton Malyshev
Anton Malyshev

Reputation: 8871

No, it does not. Attributes are not added to function signature, so you'll receive error: redefinition of 'GetCurrentIp'

The main reason is that function signatures are a characteristic of the language (C in this case), and not of the implementation (in this case gcc) that help you to match them in the expressions, so there must be no implementation dependency there. And attributes (like the one you mention, a hint for the compiler to never expand that function inline) are directives to the compiler to generate the code as you want. Indeed, attributes as defined by gcc are not a characteristic of the language, and as such program meaning should not change by the inclusion or exclusion of these.

Upvotes: 1

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