Package: g++-12
Version: 12.2.0-14
Severity: normal
X-Debbugs-Cc: iv...@isle.spb.ru
Dear Maintainer,
When I compile c++ code which has an error (method invoked on
null class pointer) the following problem occurs: the actual
call does not crash, since 'this' pointer is not really used
in called method, but conditional below works incorrectly.
Here's the simplified code in question:
else {
np = getstr(cp);
if (!::strcasecmp(np, "info"))
current = channel->get_class(ErrorCode::Info);
else if (!::strcasecmp(np, "internal"))
current = channel->get_class(ErrorCode::Internal);
. . . . . .
else {
Log::Error("%s:%d: unrecognized error class [%s]", _fname, _lineno,
np);
current = 0;
continue;
}
}
if (!channel || !current)
continue;
np = getstr(cp);
channel can be 0 after first 'else', but get_class() does not crash,
since it just returns a computed pointer to array item inside the
object, so that current is set to some invalid value like 0x120.
It proceeds to the 'if (!channel || !current)' conditional and
with given values (channel == 0, current == 0x120) continue should
be executed. Instead the control falls through to the next line.
This error occurs only when the code is compiled with -O2 or -O3.
When -O0 is used, the conditional works properly. The error is
not observed when compiled with g++-11.
The error also dissappears when I fix my error (replace first
'else {' by 'else if (channel) {').
If this information is of any interest I can send combined
c++/assembly listings for cases with and without optimization.
Best regards,
-- System Information:
Debian Release: 12.0
APT prefers stable-security
APT policy: (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 5.10.0-23-amd64 (SMP w/2 CPU threads)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8),
LANGUAGE=en_US:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages g++-12 depends on:
ii gcc-12 12.2.0-14
ii gcc-12-base 12.2.0-14
ii libc6 2.36-9
ii libgmp10 2:6.2.1+dfsg1-1.1
ii libisl23 0.25-1
ii libmpc3 1.3.1-1
ii libmpfr6 4.2.0-1
ii libstdc++-12-dev 12.2.0-14
ii libzstd1 1.5.4+dfsg2-5
ii zlib1g 1:1.2.13.dfsg-1
g++-12 recommends no packages.
Versions of packages g++-12 suggests:
pn g++-12-multilib <none>
pn gcc-12-doc <none>
-- no debconf information
