[Bug preprocessor/58770] New: GCC very slow compiling with #pragma once

["yellow at rg3 dot name" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58770

            Bug ID: 58770
           Summary: GCC very slow compiling with #pragma once
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yellow at rg3 dot name

Created attachment 31026
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31026&action=edit
Benchmark files

Putting #pragma once in a header file, with or without additional classic
include guards, makes GCC very slow.

I've created a small benchmark that I'm attaching, with the following files:

* common.h: a common file to be included 10,000 times, protected with guards or
the pragma. In the tarball there are three versions to be tested.

* header0000.h to header9999.h: header files that include common.h

* all.h: header file that includes all header????.h files.

* main.c: main program, includes common.h and all.h

Building that program with gcc -o main main.c takes 1.5 seconds with #pragma
once, while merely using include guards takes only 70 milliseconds.