[Bug c/46073] New: __builtin_choose_expr outputs warnings for unused expression

[kevin.waugh at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46073

   Summary: __builtin_choose_expr outputs warnings for unused
expression
   Product: gcc
   Version: 4.0.1
Status: UNCONFIRMED
  Severity: minor
  Priority: P3
 Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: kevin.wa...@gmail.com


$ gcc -std=c99 -Wall -x c - << EOF
void A(int * p) {}
void B(double * p) {}
int main() {
  int * p = 0;
  __builtin_choose_expr(__builtin_types_compatible_p(__typeof__(p), int *),
A(p), B(p));
  return 0;
}
EOF
: In function ‘main’:
:5: warning: passing argument 1 of ‘B’ from incompatible pointer type

$ gcc -v
Using built-in specs.
Target: i686-apple-darwin9
Configured with: /var/tmp/gcc/gcc-5493~1/src/configure --disable-checking
-enable-werror --prefix=/usr --mandir=/share/man
--enable-languages=c,objc,c++,obj-c++
--program-transform-name=/^[cg][^.-]*$/s/$/-4.0/
--with-gxx-include-dir=/include/c++/4.0.0 --with-slibdir=/usr/lib
--build=i686-apple-darwin9 --with-arch=apple --with-tune=generic
--host=i686-apple-darwin9 --target=i686-apple-darwin9
Thread model: posix
gcc version 4.0.1 (Apple Inc. build 5493)

[Bug c/46073] __builtin_choose_expr outputs warnings for unused expression

[kevin.waugh at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46073

--- Comment #2 from kevin.waugh at gmail dot com 2010-10-18 19:17:17 UTC ---
(In reply to comment #1)
> I think this is correct as  __builtin_choose_expr still does semantically
> checking on the two arguments.  Not to mention  __builtin_choose_expr was 
> added
> only to support Altivec intrinsics and that has since been moved away from
> that.

>From the documentation:
Note: This construct is only available for C. Furthermore, the unused
expression (exp1 or exp2 depending on the value of const_exp) may still
generate syntax errors. This may change in future revisions.

What are the chances of getting this changed, or having an option to suppress
warnings on the unevaluated argument?  The implementation of tgmath.h is
essentially using __builtin_choose_expr for the same purpose, but it appers to
avoid any warnings/errors because of implicit casts.

[Bug other/49666] New: passing nested function to inline function causes a trampoline call

[kevin.waugh at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49666

   Summary: passing nested function to inline function causes a
trampoline call
   Product: gcc
   Version: 4.6.0
Status: UNCONFIRMED
  Severity: enhancement
  Priority: P3
 Component: other
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: kevin.wa...@gmail.com


#include 
static inline int identity(int (*f)()) {
  return f();
}

int n = 0;
int f() {
  return n;
}

int main() {
  int m = 0;
  int g() {
return m;
  }
  printf("%d\n", identity(f)); /* inlines all the way */
  printf("%d\n", identity(g)); /* calls g through trampoline */
  printf("%d\n", g()); /* inline's g */
}