[Bug c/108964] New: Attribute target should be implemented for C backend (not only c++)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108964
Bug ID: 108964
Summary: Attribute target should be implemented for C backend
(not only c++)
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: rouca at debian dot org
Target Milestone: ---
Hi,
The following program fail to compile with gcc but compile with g++
On the debian side we will like to have it see
https://wiki.debian.org/InstructionSelection
__attribute__((target("default")))
int test_fn()
{
return 1;
}
__attribute__((target("sse2")))
int test_fn()
{
return 0;
}
int main()
{
return test_fn();
}
Bastien (rouca for debian)
[Bug c/109214] New: extension to C language allowing void * to be cast to function pointer should be documented
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109214 Bug ID: 109214 Summary: extension to C language allowing void * to be cast to function pointer should be documented Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: rouca at debian dot org Target Milestone: --- Hi, according to POSIX https://pubs.opengroup.org/onlinepubs/009696899/functions/dlsym.html "The ISO C standard does not require that pointers to functions can be cast back and forth to pointers to data. Indeed, the ISO C standard does not require that an object of type void * can hold a pointer to a function. Implementations supporting the XSI extension, however, do require that an object of type void * can hold a pointer to a function. The result of converting a pointer to a function into a pointer to another data type (except void *) is still undefined, however. Note that compilers conforming to the ISO C standard are required to generate a warning if a conversion from a void * pointer to a function pointer is attempted as in: fptr = (int (*)(int))dlsym(handle, "my_function");" This extension should be documented in the C, C++ extension documentation. Moreover maybe adding a type attribute in order to clear the warning for this kind of function may also help [1] Bastien [1] https://stackoverflow.com/questions/31526876/casting-when-using-dlsym
[Bug c/109214] extension to C language allowing void * to be cast to function pointer should be documented
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109214 --- Comment #1 from rouca --- According to my C standard: 6.3.2.3 Pointers 1 A pointer to void may be converted to or from a pointer to any incomplete or object type. A pointer to any incomplete or object type may be converted to a pointer to void and back again; the result shall compare equal to the original pointer. [...] 8. A pointer to a function of one type may be converted to a pointer to a function ofanother type and back again; the result shall compare equal to the original pointer. If a converted pointer is used to call a function whose type is not compatible with the pointed-to type, the behavior is undefined Note that I work due to implementation of J - Portability issues, §J.5.7 Function pointer cast (informative) J.5.7 Function pointer casts 1 A pointer to an object or to void may be cast to a pointer to a function, allowing data to be invoked as a function (6.5.4). 2 A pointer to a function may be cast to a pointer to an object or to void, allowing a function to be inspected or modified (for example, by a debugger) (6.5.4).
[Bug c/108964] Attribute target should be implemented for C backend (not only c++)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108964 rouca changed: What|Removed |Added Version|12.2.0 |14.0 --- Comment #1 from rouca --- Hi, On the debian side we will really like to have it.
