From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-432061-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 11989 invoked by alias); 17 Oct 2013 17:11:53 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
Received: (qmail 11385 invoked by uid 48); 17 Oct 2013 17:11:48 -0000
From: "yellow at rg3 dot name" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug preprocessor/58770] New: GCC very slow compiling with #pragma once
Date: Thu, 17 Oct 2013 17:11:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: preprocessor
X-Bugzilla-Version: 4.8.1
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: yellow at rg3 dot name
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter attachments.created
Message-ID: <bug-58770-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2013-10/txt/msg01205.txt.bz2

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.