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Issues w/ cross-compiling

From: Philip A. Prindeville
Subject: Issues w/ cross-compiling
Date: Mon, 07 Jul 2008 23:52:31 -0700
User-agent: Thunderbird (Windows/20080421)

I was wondering who I might work with to resolve some issues having to do with cross-compilation.

For instance, sometimes building i386 targets on x64 architecture will cause issues, or else building i586-uClibc targets on FC7 and x64 will cause the compiler to make broken assumptions about what the target sizes are for "int", "long", "long long", etc.

Looking at sequences like:

echo $ac_n "checking size of size_t""... $ac_c" 1>&6
echo "configure:17119: checking size of size_t" >&5
if eval "test \"`echo '$''{'ac_cv_sizeof_size_t'+set}'`\" = set"; then
 echo $ac_n "(cached) $ac_c" 1>&6
 if test "$cross_compiling" = yes; then

which comes from:

build_i586/php-5.2.6/, 8)

and is more than a little suspect.

May I suggest that the 2nd argument to AC_CHECK_SIZEOF() is an extremely bad idea, and should be banished post haste?

And if you have a include/bits/types.h file to search from, why not grab the sizes (in bits) of various types directly from there? (True, this is a linuxism.... I'm sure a lot of other platforms have similar headers we can tailor to...)

Looking at this file on a particular cross-development project I'm working on, I see:

typedef signed char __int8_t;
typedef unsigned char __uint8_t;
typedef signed short int __int16_t;
typedef unsigned short int __uint16_t;
typedef signed int __int32_t;
typedef unsigned int __uint32_t;

I can surmise correctly that the default value for AC_CHECK_SIZEOF(unsigned int) should be 4, for instance.

Or from:

typedef signed int __int32_t;
typedef int __ssize_t; /* Type of a byte count, or error. */

Ok, slightly more work, but AC_CHECK_SIZEOF(size_t) should be 4 also. (Yes, I left out a step involving bits/kernel_types.h...)

At a minimum, could we add a flag to autoconf that would cause it to fail if it encountered any instances of AC_CHECK_SIZEOF() with a second argument...

I noticed some other issues with cross-compilation in various packages, but there doesn't seem to be an easy fix to this.

If I have time, I'll try to triage the sorts of frequent failures to accommodate cross-compilation that I encounter, and see if there's any sort of commonality that we could exploit...



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