On Thu, May 14, 2020 at 4:19 PM Geoff Mulligan <ge...@mulligan.com> 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 <stdio.h>
>
> 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
>
