[Bug c++/101126] New: Enabling modules suppresses creation of precompiled headers

[Bug c++/101126] New: Enabling modules suppresses creation of precompiled headers

[overlord624 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101126

            Bug ID: 101126
           Summary: Enabling modules suppresses creation of precompiled
                    headers
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: overlord624 at gmail dot com
  Target Milestone: ---

The output of a precompiled header is suppressed if modules are enabled via
-fmodules-ts. This can be reproduced with the following invocation using any
valid input:
g++-11 -x c++-header -std=c++20 -fmodules-ts -o header.hpp.gch header.hpp

As described in the manual, -fmodules-ts implicitly sets -fmodule-header when
the input is a header file which results in the creation of a compiled header
unit in the module cache and causes the output parameter to be silently ignored
as a side effect.

-----
$ g++-11 -v
Using built-in specs.
COLLECT_GCC=g++-11
COLLECT_LTO_WRAPPER=/media/extra/libexec/gcc/x86_64-pc-linux-gnu/11.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /media/extra/sources/gcc/configure --host=x86_64-pc-linux-gnu
--prefix=/media/extra --disable-multilib --enable-threads --enable-tls
--enable-languages=c,c++ --disable-nls
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.0.1 20210402 (experimental) (GCC)