https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91893
Bug ID: 91893
Summary: Bit-field larger than 32 bits has invalid type
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: alex_lop at walla dot com
Target Milestone: ---
Example: https://godbolt.org/z/4JJtTr
#include <stdint.h>
#include <assert.h>
#define CHECK_NUM(num) _Generic((num), \
uint64_t : 0, \
int64_t : 0, \
default : 1)
int main(void)
{
struct _s
{
uint64_t val : 33; // this cannot be held in unsigned int
} s;
static_assert(CHECK_NUM(s.val), "Variable too large #1"); //
Compilation should fail here
(void)s;
return 0;
}
Based on the C11 standard section 6.3.1.1 Boolean, characters and integers :
"If an int can represent all values of the original type (as restricted by the
width, for a bit-field), the value is converted to an int; otherwise, it is
converted to an unsigned int. These are called the integer promotions.) All
other types are unchanged by the integer promotions."
I would expect _Generic((s.val), ...) to return 0 for uint64_t in this case.
Note: might be related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84516
----------------------------
Compiler configuration:
Using built-in specs.
COLLECT_GCC=/opt/compiler-explorer/gcc-9.2.0/bin/gcc
Target: x86_64-linux-gnu
Configured with: ../gcc-9.2.0/configure
--prefix=/opt/compiler-explorer/gcc-build/staging --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu --disable-bootstrap
--enable-multiarch --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --enable-clocale=gnu --enable-languages=c,c++,fortran,ada
--enable-ld=yes --enable-gold=yes --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-linker-build-id --enable-lto
--enable-plugins --enable-threads=posix
--with-pkgversion=Compiler-Explorer-Build
Thread model: posix
gcc version 9.2.0 (Compiler-Explorer-Build)
COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-g' '-o' './output.s'
'-masm=intel' '-S' '-O3' '-std=c11' '-Wall' '-m32' '-Wpedantic' '-Wextra' '-v'
'-mtune=generic' '-march=x86-64'
/opt/compiler-explorer/gcc-9.2.0/bin/../libexec/gcc/x86_64-linux-gnu/9.2.0/cc1
-quiet -v -imultilib 32 -imultiarch i386-linux-gnu -iprefix
/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/
<source> -quiet -dumpbase example.c -masm=intel -m32 -mtune=generic
-march=x86-64 -auxbase-strip ./output.s -g -O3 -Wall -Wpedantic -Wextra
-std=c11 -version -fdiagnostics-color=always -o ./output.s
GNU C11 (Compiler-Explorer-Build) version 9.2.0 (x86_64-linux-gnu)
compiled by GNU C version 7.4.0, GMP version 6.1.0, MPFR version 3.1.4,
MPC version 1.0.3, isl version isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory
"/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/../../../../x86_64-linux-gnu/include"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/9.2.0/include"
ignoring nonexistent directory "/usr/local/include/i386-linux-gnu"
ignoring duplicate directory
"/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/9.2.0/include-fixed"
ignoring nonexistent directory
"/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/../../lib/gcc/x86_64-linux-gnu/9.2.0/../../../../x86_64-linux-gnu/include"
ignoring nonexistent directory "/usr/include/i386-linux-gnu"
#include "..." search starts here:
#include <...> search starts here:
/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/include
/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/include-fixed
/usr/local/include
/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/../../include
/usr/include
End of search list.
GNU C11 (Compiler-Explorer-Build) version 9.2.0 (x86_64-linux-gnu)
compiled by GNU C version 7.4.0, GMP version 6.1.0, MPFR version 3.1.4,
MPC version 1.0.3, isl version isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: eb31180ed62a495914b9b0bdb15992b1
COMPILER_PATH=/opt/compiler-explorer/gcc-9.2.0/bin/../libexec/gcc/x86_64-linux-gnu/9.2.0/:/opt/compiler-explorer/gcc-9.2.0/bin/../libexec/gcc/:/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/../../../../x86_64-linux-gnu/bin/
LIBRARY_PATH=/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/32/:/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/../../../../lib32/:/lib/i386-linux-gnu/:/lib/../lib32/:/usr/lib/i386-linux-gnu/:/usr/lib/../lib32/:/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/:/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/:/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/../../../../x86_64-linux-gnu/lib/:/opt/compiler-explorer/gcc-9.2.0/bin/../lib/gcc/x86_64-linux-gnu/9.2.0/../../../:/lib/i386-linux-gnu/:/lib/:/usr/lib/i386-linux-gnu/:/usr/lib/
COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-g' '-o' './output.s'
'-masm=intel' '-S' '-O3' '-std=c11' '-Wall' '-m32' '-Wpedantic' '-Wextra' '-v'
'-mtune=generic' '-march=x86-64'
Compiler returned: 0
