mingw/cygwin alignment-problem in executables (ld & as)

[Sergey R. Grigoriev]

Hi BFD and GAS Gurus!


Using gcc's __attribute__((align(16))) functionality (nessesary for sse2
and partially sse, and to have working -malign-doubles in GCC) results 
in the compiler correctly generating .align directives.
They are not ignored by the assembler and generated symbols are properly
aligned in single object-file. But the sizes of data-sections in object 
files are not 16-byte aligned.

GAS try to rallign sections (for each .align XXX in input) but it seems 
to not affects output... at least objdump does shows the same 
section-alignement (i.e. 2**2) as without ".align 16" directive.

Linked by ld (not all data sections have 16-byte-aligned size) it will 
be no more aligned in resuling data segments.

I think there is 2 possible solutions:
1. Align all data-sections sizes to 16-byte
2. Store alignement information in object-files and ling it properly.

Unfortunately I have no knoledge how BFD works (i.e. what information is 
stored in object-file header) and how it interacts with GAS...

As workaround (and probably as fix) I copied the part of coff-go32.c 
file into pe-i386.c and pei-i386.c files in BFD-library to force gas to 
produce 16-bytes aligned data-segments like it is done for i386-GO32 
platform.

I need to know if it is right method to do 16-byte alignment of all 
data-segments (i.e. forcing BFD to aling it don't break anything) or how 
to do it properly?


/***********************************************/

bfd/pei-i386.c:
bfd/pe-i386.c:

#define COFF_LONG_FILENAMES

#define COFF_SECTION_ALIGNMENT_ENTRIES \
{ COFF_SECTION_NAME_EXACT_MATCH (".bss"), \
   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 4 }, \
{ COFF_SECTION_NAME_EXACT_MATCH (".data"), \
   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 4 }, \
{ COFF_SECTION_NAME_EXACT_MATCH (".text"), \
   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 4 }, \
{ COFF_SECTION_NAME_PARTIAL_MATCH (".idata"), \
   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 2 }, \
{ COFF_SECTION_NAME_EXACT_MATCH (".pdata"), \
   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 2 }

#include "coff-i386.c"