linux-ext4 - Re: [PATCH 1/5] misc: enable link time optimization, if requested

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Date:   Sun, 25 Mar 2018 01:38:20 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/5] misc: enable link time optimization, if requested

On Fri, Mar 23, 2018 at 06:57:42PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@...cle.com>
> 
> Enable link time optimization (LTO) if the builder requests it.  The
> extra link optimization results in smaller binaries.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>

Are you seeing this?  When I try compiling with --enable-lto, I'm
getting a large number of what appear to be spurious compiler warnings:

	LD e2fsck
/usr/projects/e2fsprogs/e2fsprogs-maint/lib/ext2fs/ext2fsP.h:178:13: warning: type of ‘ext2fs_warn_bitmap32’ does not match original declaration [-Wlto-type-mismatch]
 extern void ext2fs_warn_bitmap32(ext2fs_generic_bitmap bitmap,const char *func);
             ^
/usr/projects/e2fsprogs/e2fsprogs-maint/lib/ext2fs/gen_bitmap64.c:745:6: note: ‘ext2fs_warn_bitmap32’ was previously declared here
 void ext2fs_warn_bitmap32(ext2fs_generic_bitmap bitmap, const char *func)
      ^
/usr/projects/e2fsprogs/e2fsprogs-maint/lib/ext2fs/gen_bitmap64.c:745:6: note: code may be misoptimized unless -fno-strict-aliasing is used
/usr/projects/e2fsprogs/e2fsprogs-maint/lib/ext2fs/bitops.h:106:13: warning: type of ‘ext2fs_unmark_block_bitmap_range’ does not match original declaration [-Wlto-type-mismatch]
 extern void ext2fs_unmark_block_bitmap_range(ext2fs_block_bitmap bitmap,
             ^
/usr/projects/e2fsprogs/e2fsprogs-maint/lib/ext2fs/gen_bitmap.c:593:6: note: ‘ext2fs_unmark_block_bitmap_range’ was previously declared here
 void ext2fs_unmark_block_bitmap_range(ext2fs_block_bitmap bitmap,
      ^
/usr/projects/e2fsprogs/e2fsprogs-maint/lib/ext2fs/gen_bitmap.c:593:6: note: code may be misoptimized unless -fno-strict-aliasing is used
   ...


This is using gcc version: gcc (Debian 7.3.0-12) 7.3.0

     	      	  	       	       		 - Ted