https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104012
Bug ID: 104012
Summary: -Wformat-truncation warnings not taking previous
length check into account
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: e...@sf-mail.de
Target Milestone: ---
This code is from CMake's Source/cmLocalUnixMakefileGenerator3.cxx:
std::string cmLocalUnixMakefileGenerator3::CreateMakeVariable(
std::string const& s, std::string const& s2)
{
[…]
char buffer[5];
int ni = 0;
snprintf(buffer, sizeof(buffer), "%04d", ni);
ret = str1 + str2 + buffer;
while (this->ShortMakeVariableMap.count(ret) && ni < 1000) {
++ni;
snprintf(buffer, sizeof(buffer), "%04d", ni);
ret = str1 + str2 + buffer;
}
The second snprintf() causes this warning:
…/CMake/Source/cmLocalUnixMakefileGenerator3.cxx:1311:41: warning: '%04d'
directive output may be truncated writing between 4 and 11 bytes into a region
of size 5 [-Wformat-truncation=]
1311 | snprintf(buffer, sizeof(buffer), "%04d", ni);
| ^~~~
…/CMake/Source/cmLocalUnixMakefileGenerator3.cxx:1311:40: note: directive
argument in the range [-2147483647, 2147483647]
1311 | snprintf(buffer, sizeof(buffer), "%04d", ni);
| ^~~~~~
The second warning line shows that the argument range is not correctly limited
to [0, 1000], which would have avoided the warning. A similar warning is shown
~30 lines earlier in the same file for basically the same code.
My current version is:
gcc-12.0.0 (Gentoo 12.0.0_pre9999 p2, commit
8b35f02ed599a70cce752e3cb544a7c9f808fce8) 12.0.0 20220111 (experimental)
The version used previously has been built on 2021-08-14T20:47:39 and didn't
show that warning.
