[fixed in 4.5] -Wunused-value cannot be suppressed

[Stanislaw Pitucha]

Some functions that have warn-unused-result cannot be used in a way described in http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Warning-Options.html

For example this line (where STDOUT_FILENO==0 and FLAG_EXIT_NOW is defined as some string):
(void) write(STDOUT_FILENO, FLAG_EXIT_NOW, sizeof FLAG_EXIT_NOW - 1);

compiled with:

cc -g -O -W -Wall -Wno-system-headers -Werror -Wunused-parameter -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wcast-align -Wunused-parameter -Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls -c ....

will report "error: ignoring return value of ‘write’, declared with attribute warn_unused_result". According to gcc docs, casting to (void) should prevent that.

ProblemType: Bug
Architecture: i386
Date: Thu Nov 5 22:31:44 2009
DistroRelease: Ubuntu 9.10
Package: gcc 4:4.4.1-1ubuntu2
ProcEnviron:
 LANGUAGE=pl_PL.UTF-8
 PATH=(custom, no user)
 LANG=pl_PL.UTF-8
 SHELL=/bin/zsh
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: gcc-defaults
Uname: Linux 2.6.31-14-generic i686

[Matthias Klose (doko)]

fixed in 4.5 (available as gcc-snapshot in lucid)