[Bug c/89448] New: Failure to generate diagnostic for "complex int" (OK for "_Complex int")

[mrison at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89448

            Bug ID: 89448
           Summary: Failure to generate diagnostic for "complex int" (OK
                    for "_Complex int")
           Product: gcc
           Version: 7.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mrison at hotmail dot com
  Target Milestone: ---

$ cat complex.c
#include <complex.h>
int lower (void)
{
  complex int a = 0;
  return creal (a);
}
int upperunder (void)
{
  _Complex int a = 0;
  return creal (a);
}
int redef (void)
{
#undef complex
#define complex _Complex
  complex int a = 0;
  return creal (a);
}
$ gcc -std=c99 -pedantic -c complex.c
complex.c: In function ‘upperunder’:
complex.c:9:3: warning: ISO C does not support complex integer types
[-Wpedantic]
   _Complex int a = 0;
   ^~~~~~~~
complex.c: In function ‘redef’:
complex.c:15:17: warning: ISO C does not support complex integer types
[-Wpedantic]
 #define complex _Complex
                 ^
complex.c:16:3: note: in expansion of macro ‘complex’
   complex int a = 0;
   ^~~~~~~
$

Why no diagnostic in lower() but yes in redef()?  Sounds as if the
"complex" from <complex.h> is not just "_Complex".

The preprocessed form just further confuses the matter, because (as expected)
"complex" does appear to be just "_Complex":

# 2 "complex.c"
int lower (void)
{

# 4 "complex.c" 3 4
 _Complex
# 4 "complex.c"
         int a = 0;
  return creal (a);
}

I am using gcc from Ubuntu 18.04:

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/7/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
7.3.0-27ubuntu1~18.04' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-7
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --with-target-system-zlib --enable-objc-gc=auto
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04)

Thanks,

Mark