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* [Bug c/101125] New: warn when a construct would become invalid if a function were replaced by a function-like macro
@ 2021-06-18 14:38 vincent-gcc at vinc17 dot net
2021-06-18 17:00 ` [Bug c/101125] " pinskia at gcc dot gnu.org
2021-06-18 19:15 ` vincent-gcc at vinc17 dot net
0 siblings, 2 replies; 3+ messages in thread
From: vincent-gcc at vinc17 dot net @ 2021-06-18 14:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101125
Bug ID: 101125
Summary: warn when a construct would become invalid if a
function were replaced by a function-like macro
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: vincent-gcc at vinc17 dot net
Target Milestone: ---
In the standard C library and some other libraries (like GNU MPFR), functions
may be replaced by function-like macros with the same behavior. So, in order to
detect potential portability issues, GCC should provide a warning to check
whether a construct used with a function call would become invalid if the
function were replaced by a macro.
Such a difference can at least come from the use of the comma in some
expressions. Example:
struct s { int a, b; };
void f (int);
#define F(X) f(X)
void g (void)
{
f ((struct s){0,1}.a);
F ((struct s){0,1}.a);
}
The call to f is valid, but the use of the macro yields an error because the
preprocessor assumes that there are 2 arguments in the call: "(struct s){0" and
"1}.a". Here, one should use additional parentheses:
F (((struct s){0,1}.a));
AFAIK, the library (which provides the function and the macro in a header file)
cannot do anything to avoid such an error; only the user can avoid it, but he
may not be aware of the issue as long as only a function is provided. Hence the
usefulness of the proposed warning.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/101125] warn when a construct would become invalid if a function were replaced by a function-like macro
2021-06-18 14:38 [Bug c/101125] New: warn when a construct would become invalid if a function were replaced by a function-like macro vincent-gcc at vinc17 dot net
@ 2021-06-18 17:00 ` pinskia at gcc dot gnu.org
2021-06-18 19:15 ` vincent-gcc at vinc17 dot net
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-06-18 17:00 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101125
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Keywords| |diagnostic
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I really doubt this is an useful warning really. GCC has already had a notion
that inline functions should be as fast as macro functions and type safe ...
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/101125] warn when a construct would become invalid if a function were replaced by a function-like macro
2021-06-18 14:38 [Bug c/101125] New: warn when a construct would become invalid if a function were replaced by a function-like macro vincent-gcc at vinc17 dot net
2021-06-18 17:00 ` [Bug c/101125] " pinskia at gcc dot gnu.org
@ 2021-06-18 19:15 ` vincent-gcc at vinc17 dot net
1 sibling, 0 replies; 3+ messages in thread
From: vincent-gcc at vinc17 dot net @ 2021-06-18 19:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101125
--- Comment #2 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
Even though GCC support fast inline functions, some libraries may still use
function-like macros. In particular, this is still the case with glibc (e.g.
pthread_cleanup_pop).
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-06-18 19:15 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-06-18 14:38 [Bug c/101125] New: warn when a construct would become invalid if a function were replaced by a function-like macro vincent-gcc at vinc17 dot net
2021-06-18 17:00 ` [Bug c/101125] " pinskia at gcc dot gnu.org
2021-06-18 19:15 ` vincent-gcc at vinc17 dot net
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