https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107466
Bug ID: 107466
Summary: [12 Regression] invalid -Wnarrowing error
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: littlefox+gcc-bugzi...@lf-net.org
Target Milestone: ---
Created attachment 53797
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53797&action=edit
Code triggering the error
Hi,
the attached code (and Godbolt[1]) fails in gcc 12+ with an -Wnarrowing error
in a stdlibc++ template instantiated with an uint16_t and apparently trying to
work with a 2^31:
/opt/compiler-explorer/gcc-12.2.0/include/c++/12.2.0/bits/random.tcc:545:9:
error: narrowing conversion of '2147483563' from 'unsigned int' to 'short
unsigned int' [-Wnarrowing]
545 | __lcg(__value == 0u ? default_seed : __value);
The code works fine in 11.3 and clang (14) and since it also works in clang
using libstdc++ 12.2, this error is probably in gcc itself and not in
libstdc++.
Tested this on my machine (debian testing), where it broke after a some system
updates where installed - including a gcc update. Then tested this in Godbolt
to check compiler versions and other configurations and asked in
libera.chat/#c++ for others to verify if my code makes sense - which it seems
to do.
Best, Mara
[1] Godbolt link: https://godbolt.org/z/sj18Mv5j9
