https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79750
Bug ID: 79750
Summary: -Wimplicit-fallthrough= comment detection gets
confused by #if
Product: gcc
Version: 7.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: sgunderson at bigfoot dot com
Target Milestone: ---
Hi,
It seems that fallthrough comments are not properly parsed if they are followed
by a preprocessor statement. Minified test case:
atum17:~> /usr/lib/gcc-snapshot/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/usr/lib/gcc-snapshot/bin/g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc-snapshot/libexec/gcc/x86_64-linux-gnu/7/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 20170226-1'
--with-bugurl=file:///usr/share/doc/gcc-snapshot/README.Bugs
--enable-languages=c,ada,c++,go,brig,fortran,objc,obj-c++
--prefix=/usr/lib/gcc-snapshot --with-gcc-major-version-only --program-prefix=
--enable-shared --enable-linker-build-id --disable-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 --with-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-checking=yes --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 7.0.1 20170226 (experimental) [trunk revision 245744] (Debian
20170226-1)
atum17:~> cat test.cc
int func(int x)
{
switch (x) {
case 0:
x = 1;
//-fallthrough
#if 1
case 1:
#endif
case 2:
++x;
}
return x;
}
atum17:~> /usr/lib/gcc-snapshot/bin/g++ -Wall -Wextra -c test.cc
test.cc: In function 'int func(int)':
test.cc:5:5: warning: this statement may fall through [-Wimplicit-fallthrough=]
x = 1;
~~^~~
test.cc:8:2: note: here
case 1:
^~~~
If I remove the #if 1, there is no warning.
