https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81417
Bug ID: 81417
Summary: -Wsign-compare should print types being compared
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: egall at gwmail dot gwu.edu
Target Milestone: ---
Host: i386-apple-darwin9.8.0
Target: i386-apple-darwin9.8.0
Build: i386-apple-darwin9.8.0
Simple testcase:
$ cat Wsign_compare.c
/* { dg-do compile } */
int foo(signed int a, unsigned int b)
{
return (a < b);
}
When compiled with gcc, it says:
$ /usr/local/bin/gcc -c -Wsign-compare Wsign_compare.c
Wsign_compare.c: In function ‘foo’:
Wsign_compare.c:5:12: warning: comparison between signed and unsigned integer
expressions [-Wsign-compare]
return (a < b);
^
However, when compiled with clang, it gives more information:
$ /sw/opt/llvm-3.1/bin/clang -c -Wsign-compare Wsign_compare.c
Wsign_compare.c:5:12: warning: comparison of integers of different signs: 'int'
and 'unsigned int' [-Wsign-compare]
return (a < b);
~ ^ ~
1 warning generated.
In such a small file like this it might not matter much, but in bigger files
where the variables being compared are very far away from their declarations,
it can be hard to remember what types they are. Having the compiler remind me
of the types being compared would be helpful when deciding how to silence
warnings like these.
Version info:
$ /usr/local/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/local/bin/gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/i386-apple-darwin9.8.0/8.0.0/lto-wrapper
Target: i386-apple-darwin9.8.0
Configured with: ../configure --disable-werror --disable-werror-always
--enable-languages=c,c++,lto,objc,obj-c++ --enable-stage1-checking=release,rtl
-C --with-system-libunwind --enable-secureplt --enable-frame-pointer
--enable-debug --with-isl --disable-host-shared --enable-maintainer-mode
--disable-default-pie --with-ld64 --without-pic --enable-target-optspace
CC=/usr/local/bin/gcc CXX=/usr/local/bin/g++ AUTOCONF=/usr/local/bin/autoconf
AUTOHEADER=/usr/local/bin/autoheader AUTORECONF=/usr/local/bin/autoreconf
AUTOM4TE=/usr/local/bin/autom4te AUTOSCAN=/usr/local/bin/autoscan
AUTOUPDATE=/usr/local/bin/autoupdate IFNAMES=/usr/local/bin/ifnames
Thread model: posix
gcc version 8.0.0 20170702 (experimental) (GCC)
