https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98980
Bug ID: 98980
Summary: Very slow compilation with -Wduplicated-branches and
ubsan
Product: gcc
Version: 9.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: sshannin at gmail dot com
Target Milestone: ---
Created attachment 50136
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50136&action=edit
the code
I have attached a heavily reduced example which encounters excessively slow
compilation. I was not able to remove the stringstream include without the
degenerate behavior disappearing, unfortunately; I hope that's ok.
It seems to be mostly exponential in the number of operator<< invocations, with
a couple interesting behaviors
- s/long/int/g on the code allows it to compile almost instantly
- removing any of the longs being streamed seems to halve the time, but so does
replacing the variable with a literal
- removing any of the string literals also halves the time.
Compiled with flags:
/toolchain14/bin/g++ -std=c++2a -Wduplicated-branches -c -fsanitize=undefined
-o dup.o dup.cpp
/toolchain14/bin/g++ -v
Using built-in specs.
COLLECT_GCC=/toolchain14/bin/g++
COLLECT_LTO_WRAPPER=/toolchain14/libexec/gcc/x86_64-pc-linux-gnu/9.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc_9_1_0/configure --prefix=/toolchain14
--enable-languages=c,c++,fortran --enable-lto --disable-plugin
--program-suffix=-9.1.0 --disable-multilib
Thread model: posix
gcc version 9.1.0 (GCC)
