https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84502
Bug ID: 84502
Summary: Argument corruption when passing empty templated
struct
Product: gcc
Version: 8.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: patrick.schlangen at bmw dot de
Target Milestone: ---
Created attachment 43483
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43483&action=edit
Minimal example
Hi,
we've discovered a strange problem when passing many function arguments where
one argument is an alias (using = ...) for a templated struct which has no
members (e.g. std::integer_sequence).
When building in non-optimized mode or with -O1/-O2, all arguments starting
from argument #7 seem to be corrupt. Building with -O3 seems to solve the
issue.
I've attached a small example program.
Correct output:
---------------
$ ~/gcc-8/bin/g++ -O3 -o repro repro.cpp && ./repro
0, 1, 2, 3, 4, 5, 6, 7
Wrong outputs:
--------------
$ ~/gcc-8/bin/g++ -O2 -o repro repro.cpp && ./repro
0, 1, 2, 3, 4, 5, 7, 0
$ ~/gcc-8/bin/g++ -O1 -o repro repro.cpp && ./repro
0, 1, 2, 3, 4, 5, 7, 0
$ ~/gcc-8/bin/g++ -O0 -o repro repro.cpp && ./repro
0, 1, 2, 3, 4, 5, 7, 2088590376
gcc version (freshly built):
----------------------------
$ ~/gcc-8/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/home/patrick/gcc-8/bin/g++
COLLECT_LTO_WRAPPER=/home/patrick/gcc-8/libexec/gcc/x86_64-pc-linux-gnu/8.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ./configure --prefix=/home/patrick/gcc-8 --disable-multilib
Thread model: posix
gcc version 8.0.1 20180218 (experimental) (GCC)
Best Regards
Patrick
