https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83696
Bug ID: 83696
Summary: false positive warning when [[fallthrough]] is inside
of if statement
Product: gcc
Version: 7.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: shyou...@ruby-lang.org
Target Milestone: ---
Created attachment 43038
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43038&action=edit
reproducible code
It seems [[fallthrough]] does not take effect when it is inside of an if
statement who has || in the expression.
% cat tmp.cpp
#pragma GCC diagnostic error "-Wimplicit-fallthrough"
int
func(int i, int j)
{
switch (i) {
case 0:
if ( i || j )
return 1;
else
[[fallthrough]];
default:
return 0;
}
}
% gcc-7 -v -std=c++17 tmp.cpp
Using built-in specs.
COLLECT_GCC=gcc-7
COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc/7.2.0/libexec/gcc/x86_64-apple-darwin15.6.0/7.2.0/lto-wrapper
Target: x86_64-apple-darwin15.6.0
Configured with: ../configure --build=x86_64-apple-darwin15.6.0
--prefix=/usr/local/Cellar/gcc/7.2.0
--libdir=/usr/local/Cellar/gcc/7.2.0/lib/gcc/7
--enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-7
--with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr
--with-mpc=/usr/local/opt/libmpc --with-isl=/usr/local/opt/isl
--with-system-zlib --enable-checking=release --with-pkgversion='Homebrew GCC
7.2.0' --with-bugurl=https://github.com/Homebrew/homebrew-core/issues
--disable-nls
Thread model: posix
gcc version 7.2.0 (Homebrew GCC 7.2.0)
COLLECT_GCC_OPTIONS='-v' '-std=c++1z' '-mmacosx-version-min=10.11.6'
'-asm_macosx_version_min=10.11' '-mtune=core2'
/usr/local/Cellar/gcc/7.2.0/libexec/gcc/x86_64-apple-darwin15.6.0/7.2.0/cc1plus
-quiet -v -D__DYNAMIC__ tmp.cpp -fPIC -quiet -dumpbase tmp.cpp
-mmacosx-version-min=10.11.6 -mtune=core2 -auxbase tmp -std=c++1z -version -o
/var/folders/50/9ss08lxs5ml7kvz614tr3_wmm17741/T//cc2RNpgL.s
GNU C++14 (Homebrew GCC 7.2.0) version 7.2.0 (x86_64-apple-darwin15.6.0)
compiled by GNU C version 7.2.0, GMP version 6.1.2, MPFR version 3.1.5,
MPC version 1.0.3, isl version isl-0.18-GMP
warning: MPFR header version 3.1.5 differs from library version 3.1.6.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory
"/usr/local/Cellar/gcc/7.2.0/lib/gcc/7/gcc/x86_64-apple-darwin15.6.0/7.2.0/../../../../../../x86_64-apple-darwin15.6.0/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/Cellar/gcc/7.2.0/lib/gcc/7/gcc/x86_64-apple-darwin15.6.0/7.2.0/../../../../../../include/c++/7.2.0
/usr/local/Cellar/gcc/7.2.0/lib/gcc/7/gcc/x86_64-apple-darwin15.6.0/7.2.0/../../../../../../include/c++/7.2.0/x86_64-apple-darwin15.6.0
/usr/local/Cellar/gcc/7.2.0/lib/gcc/7/gcc/x86_64-apple-darwin15.6.0/7.2.0/../../../../../../include/c++/7.2.0/backward
/usr/local/Cellar/gcc/7.2.0/lib/gcc/7/gcc/x86_64-apple-darwin15.6.0/7.2.0/include
/usr/local/include
/usr/local/Cellar/gcc/7.2.0/include
/usr/local/Cellar/gcc/7.2.0/lib/gcc/7/gcc/x86_64-apple-darwin15.6.0/7.2.0/include-fixed
/usr/include
/System/Library/Frameworks
/Library/Frameworks
End of search list.
GNU C++14 (Homebrew GCC 7.2.0) version 7.2.0 (x86_64-apple-darwin15.6.0)
compiled by GNU C version 7.2.0, GMP version 6.1.2, MPFR version 3.1.5,
MPC version 1.0.3, isl version isl-0.18-GMP
warning: MPFR header version 3.1.5 differs from library version 3.1.6.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 91ccd58de1ec407f356a7036de6130ed
tmp.cpp: In function 'int func(int, int)':
tmp.cpp:8:16: error: this statement may fall through
[-Werror=implicit-fallthrough=]
if ( i || j )
~~^~~~
tmp.cpp:12:5: note: here
default:
^~~~~~~
cc1plus: some warnings being treated as errors
[1] 78552 exit 1 gcc-7 -v -std=c++17 tmp.cpp
zsh %
