https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90010
Bug ID: 90010
Summary: valgrind error with snprintf and -Wall
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dcb314 at hotmail dot com
Target Milestone: ---
For this C++ source code:
extern "C" __inline __attribute__((__gnu_inline__)) int snprintf(...) {}
class a {
char b[4096];
void c();
};
void a::c() {
char d[4096];
snprintf(d, sizeof(d), "%s/power/runtime_suspended_time", b);
}
on a valgrind version of recent gcc trunk:
$ ~/gcc/results.270150.valgrind/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/home/dcb/gcc/results.270150.valgrind/bin/g++
COLLECT_LTO_WRAPPER=/home/dcb/gcc/results.270150.valgrind/libexec/gcc/x86_64-pc-linux-gnu/9.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../trunk/configure
--prefix=/home/dcb/gcc/results.270150.valgrind --disable-bootstrap
--disable-multilib --disable-werror --enable-checking=valgrind
--enable-languages=c,c++,fortran
Thread model: posix
gcc version 9.0.1 20190404 (experimental) (GCC)
[dcb@localhost dcbTest]$
with compile flag -Wall, makes this:
$ ~/gcc/results.270150.valgrind/bin/g++ -c -Wall bug514.cc
bug514.cc:1:57: warning: declaration of ‘int snprintf(...)’ conflicts with
built-in declaration ‘int snprintf(char*, long unsigned int, const char*, ...)’
[-Wbuiltin-declaration-mismatch]
1 | extern "C" __inline __attribute__((__gnu_inline__)) int snprintf(...)
{}
| ^~~~~~~~
bug514.cc: In function ‘int snprintf(...)’:
bug514.cc:1:72: warning: no return statement in function returning non-void
[-Wreturn-type]
1 | extern "C" __inline __attribute__((__gnu_inline__)) int snprintf(...)
{}
|
^
==30913== Conditional jump or move depends on uninitialised value(s)
==30913== at 0x483BB9D: strnlen (vg_replace_strmem.c:428)
==30913== by 0x137D3F3: pp_format(pretty_printer*, text_info*)
(pretty-print.c:1374)
==30913== by 0x1373D62: diagnostic_report_diagnostic(diagnostic_context*,
diagnostic_info*) (diagnostic.c:1015)
==30913== by 0xB5F828: format_string_diagnostic_t::emit_warning_n_va(int,
unsigned long, char const*, char const*, __va_list_tag (*) [1]) const
(substring-locations.c:216)
