Re: bug in bit structure compilation
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Re: bug in bit structure compilation
On Thu, May 14, 2020 at 4:19 PM Geoff Mulligan wrote:
>
> Version:
> 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
> 7.5.0-3ubuntu1~18.04'
> --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 --enable-bootstrap --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 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
>
> Here is a simple program:
>
> #include
>
> int main() {
>struct {
> int a : 3;
>} foo;
>
>switch (foo.a) {
>case 3: break;
>case 4: break;
>}
>
>if (foo.a == 3) { }
>if (foo.a == 4) { }
> }
>
> When compiling the compiler complains:
> gcc -o a a.c
> a.c: In function ‘main’:
> a.c:10:3: warning: case label value exceeds maximum value for type
> case 4: break;
> ^~~~
>
> It would seem that 4 is within the bounds of 0 to 7.
But the range of foo.a is -4 ... 3 and not 0 ... 7.
>
> Geoff
>
Re: bug in bit structure compilation
Obviously I'm an idiot. signed vs unsigned. Ugh. But maybe the
compiler should complain about the if test...
Geoff
On 5/14/20 4:45 PM, Geoff Mulligan wrote:
Version:
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
7.5.0-3ubuntu1~18.04'
--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 --enable-bootstrap --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 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
Here is a simple program:
#include
int main() {
struct {
int a : 3;
} foo;
switch (foo.a) {
case 3: break;
case 4: break;
}
if (foo.a == 3) { }
if (foo.a == 4) { }
}
When compiling the compiler complains:
gcc -o a a.c
a.c: In function ‘main’:
a.c:10:3: warning: case label value exceeds maximum value for type
case 4: break;
^~~~
It would seem that 4 is within the bounds of 0 to 7.
Geoff
bug in bit structure compilation
Version:
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
7.5.0-3ubuntu1~18.04'
--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 --enable-bootstrap --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 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
Here is a simple program:
#include
int main() {
struct {
int a : 3;
} foo;
switch (foo.a) {
case 3: break;
case 4: break;
}
if (foo.a == 3) { }
if (foo.a == 4) { }
}
When compiling the compiler complains:
gcc -o a a.c
a.c: In function ‘main’:
a.c:10:3: warning: case label value exceeds maximum value for type
case 4: break;
^~~~
It would seem that 4 is within the bounds of 0 to 7.
Geoff
