Stack Boundary

[Mike <mgoppold5 at yahoo dot com>]

Using GCC 4.7.2 in MINGW.

Cannot figure out the code generated for " 
-mpreferred-stack-boundary=7".  If you understand the generated code, 
please explain.

I compiled a sample program I wrote (attached), disassembled it, and 
looked at the important instruction "sub esp,ALIGN_CONSTANT" in each of 
the functions.

With a -mpreferred-stack-boundary setting of 7, that means each function 
should be aligned to 128 bytes, or 0x80 bytes.

But these are the results of ALIGN_CONSTANT

FUNCTION,ALIGN_CONSTANT
start,0x178
sum,0x8C
m,0x178

I would think ALIGN_CONSTANT should be closer to 128 minus a small value 
for all 3 functions.  But 0x178 and 0x8c?

Attachment: CallingConventions.tar.gz
Description: application/gzip