From: phcoder <address@hidden>
Date: Thu, 12 Mar 2009 12:22:15 +0100
David Miller wrote:
From: phcoder <address@hidden>
Date: Thu, 12 Mar 2009 09:23:34 +0100
Index: include/grub/elf.h
===================================================================
--- include/grub/elf.h (revision 2036)
+++ include/grub/elf.h (working copy)
@@ -77,7 +77,7 @@
Elf32_Half e_shentsize; /* Section header table entry size */
Elf32_Half e_shnum; /* Section header table entry count */
Elf32_Half e_shstrndx; /* Section header string table index */
-} Elf32_Ehdr;
+} __attribute__ ((packed)) Elf32_Ehdr;
There is no reason why you should need the packed attribute here.
I can't think of any cpu where this could even remotely be necessary.
And if it's not necessary, all it does it emit terribly suboptimal
code on RISC cpus.
If it doesn't make a difference in the structure why does the compiler generate
different code?
Because packed also means that the alignment of the structure
can't be assumed to be naturally word aligned. So the compiler
has to use byte loads and stores to load a word, for example,
on RISC machines.
This is because the packed attribute influences how the structure is
embedded into other structures.
This attribute controls two different things, not just local packing.