https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81585
Bug ID: 81585
Summary: fastcall/stdcall attribute conflict not detected on
distinct declarations of the same function
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
The i386 back-end makes an effort to detect mutually exclusive function
attribute combinations such as fastcall and stdcall but it missed those that
result from merging such attributes from distinct declarations. Those then
lead to type errors later on.
The back-end also rejects these conflicting declaration with an error. That
makes sense to me but it's inconsistent with how GCC treats other such
conflicts (they are typically diagnosed with -Wattributes, with the conflicting
attribute being dropped in favor of the original; i.e., the first one wins).
$ cat x.c && gcc -O2 -S -Wall -Wextra -Wpedantic -m32 x.c
void __attribute__ ((fastcall, stdcall)) f (void);
void __attribute__ ((fastcall)) g (void);
void __attribute__ ((stdcall)) g (void);
x.c:1:1: error: stdcall and fastcall attributes are not compatible
void __attribute__ ((fastcall, stdcall)) f (void);
^~~~
x.c:5:32: error: conflicting types for ‘g’
void __attribute__ ((stdcall)) g (void);
^
x.c:3:33: note: previous declaration of ‘g’ was here
void __attribute__ ((fastcall)) g (void);
^
