Messages in this thread | | | Date | Thu, 28 Mar 2002 08:34:46 -0500 | From | Brian Gerst <> | Subject | Re: [patch] ext2_fill_super breakage |
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Andrew Morton wrote: > In 2.5.7 there is a thinko in the allocation and initialisation > of the fs-private superblock for ext2. It's passing the wrong type > to the sizeof operator (which of course gives the wrong size) > when allocating and clearing the memory. > > Lesson for the day: this is one of the reasons why this idiom: > > some_type *p; > > p = malloc(sizeof(*p)); > ... > memset(p, 0, sizeof(*p)); > > is preferable to > > some_type *p; > > p = malloc(sizeof(some_type)); > ... > memset(p, 0, sizeof(some_type)); > > I checked the other filesystems. They're OK (but idiomatically > impure). I've added a couple of defensive memsets where > they were missing.
I'm not sure I follow you here. Compiling this code (gcc 2.96):
int foo1(void) { return sizeof(struct ext2_sb_info); } int foo2(struct ext2_sb_info *sbi) { return sizeof(*sbi); }
yields:
00000b70 <foo1>: b70: b8 dc 00 00 00 mov $0xdc,%eax b75: c3 ret
00000b80 <foo2>: b80: b8 dc 00 00 00 mov $0xdc,%eax b85: c3 ret
The sizes are the same, so unless it makes a difference with another version of gcc then this is just a cosmetic change.
--
Brian Gerst
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