http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54495
Bug #: 54495
Summary: gcc gives a false warning in
kernel/trace/trace_events_filter.c
Classification: Unclassified
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: toralf.foers...@gmx.de
The current git tree of linux gave with gcc-4.6.3 :
kernel/trace/trace_events_filter.c: In function
‘ftrace_function_set_filter_cb’:
kernel/trace/trace_events_filter.c:2074:8: warning: ‘ret’ may be used
uninitialized in this function [-Wuninitialized]
which refers to this piece of code:
2002 static int __ftrace_function_set_filter(int filter, char *buf, int len,
2003 struct function_filter_data
*data)
2004 {
2005 int i, re_cnt, ret;
2006 int *reset;
2007 char **re;
2008
2009 reset = filter ? &data->first_filter : &data->first_notrace;
2010
2011 /*
2012 * The 'ip' field could have multiple filters set, separated
2013 * either by space or comma. We first cut the filter and apply
2014 * all pieces separatelly.
2015 */
2016 re = ftrace_function_filter_re(buf, len, &re_cnt);
2017 if (!re)
2018 return -EINVAL;
2019
2020 for (i = 0; i < re_cnt; i++) {
2021 ret = ftrace_function_set_regexp(data->ops, filter,
*reset,
2022 re[i], strlen(re[i]));
2023 if (ret)
2024 break;
2025
2026 if (*reset)
2027 *reset = 0;
2028 }
2029
2030 argv_free(re);
2031 return ret;
2032 }
...
2061 static int ftrace_function_set_filter_cb(enum move_type move,
2062 struct filter_pred *pred,
2063 int *err, void *data)
2064 {
2065 /* Checking the node is valid for function trace. */
2066 if ((move != MOVE_DOWN) ||
2067 (pred->left != FILTER_PRED_INVALID)) {
2068 *err = ftrace_function_check_pred(pred, 0);
2069 } else {
2070 *err = ftrace_function_check_pred(pred, 1);
2071 if (*err)
2072 return WALK_PRED_ABORT;
2073
2074 *err = __ftrace_function_set_filter(pred->op == OP_EQ,
2075
pred->regex.pattern,
2076 pred->regex.len,
2077 data);
2078 }
2079
2080 return (*err) ? WALK_PRED_ABORT : WALK_PRED_DEFAULT;
2081 }
2082
Both a kernel dev :
>Strange, as ret is initialized to 'ret = -EINVAL;' in
>__ftrace_function_set_filter(). I'm thinking that gcc got confused here.
and a Gentoo Linux User points me to file a bug about this.
I'm running an almost stable Gentoo linux :
$ gcc -v
Using built-in specs.
COLLECT_GCC=/usr/i686-pc-linux-gnu/gcc-bin/4.6.3/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/i686-pc-linux-gnu/4.6.3/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-4.6.3/work/gcc-4.6.3/configure
--prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/4.6.3
--includedir=/usr/lib/gcc/i686-pc-linux-gnu/4.6.3/include
--datadir=/usr/share/gcc-data/i686-pc-linux-gnu/4.6.3
--mandir=/usr/share/gcc-data/i686-pc-linux-gnu/4.6.3/man
--infodir=/usr/share/gcc-data/i686-pc-linux-gnu/4.6.3/info
--with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/4.6.3/include/g++-v4
--host=i686-pc-linux-gnu --build=i686-pc-linux-gnu --disable-altivec
--disable-fixed-point --without-ppl --without-cloog --enable-lto --enable-nls
--without-included-gettext --with-system-zlib --enable-obsolete
--disable-werror --enable-secureplt --disable-multilib --enable-libmudflap
--disable-libssp --enable-libgomp
--with-python-dir=/share/gcc-data/i686-pc-linux-gnu/4.6.3/python
--enable-checking=release --disable-libgcj --with-arch=i686
--enable-languages=c,c++,fortran --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu --enable-targets=all
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.6.3 p1.6,
pie-0.5.2'
Thread model: posix
gcc version 4.6.3 (Gentoo 4.6.3 p1.6, pie-0.5.2)
