From: Rob Landley <rob@landley.net>
Date: Tue, 23 Aug 2005 20:03:17 +0000 (-0000)
Subject: When compiling with FEATURE_MTAB_SUPPORT disabled, the call to erase_mtab()
X-Git-Tag: 1_1_0~813
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=f4c684a1efcf8a602d0803c889aba610b9a5ddb8;p=oweals%2Fbusybox.git

When compiling with FEATURE_MTAB_SUPPORT disabled, the call to erase_mtab()
can never be made because useMtab is initialized to 0, and all the other
assignments of that variable assign 0 to it.  Any compiler that can perform
simple constant propogation on local variables will optimize away if statements
testing against that variable, thus the call to erase_mtab() will never be
made.

When compiling for arm using gcc 3.3.3 with FEATURE_MTAB_SUPPORT disabled,
the linker complains that it can't find erase_mtab().  The arm optimizer isn't
exactly the brightest member of the family, and apparently needs to be hit over
the head with a hammer to get its' attention...
---

diff --git a/util-linux/umount.c b/util-linux/umount.c
index 6de71b4ab..dd072e7f6 100644
--- a/util-linux/umount.c
+++ b/util-linux/umount.c
@@ -116,7 +116,9 @@ extern int umount_main(int argc, char **argv)
 			del_loop(m->device);
 
 		if(curstat) {
-			if(useMtab && m) erase_mtab(m->dir);
+			/* Yes, the ENABLE is redundant here, but the optimizer for ARM
+			 * can't do simple constant propogation in local variables... */
+			if(ENABLE_FEATURE_MTAB_SUPPORT && useMtab && m) erase_mtab(m->dir);
 			status = EXIT_FAILURE;
 			bb_perror_msg("Couldn't umount %s\n", path);
 		}