php: force cross-compilation

php: force cross-compilation

In its configure script, PHP detects whether we're cross-compiling or

not, by compiling and running a simple C program. Depending on whether

cross-compiling has been detected or not, then PHP enables or disables

the AC_TRY_RUN tests (which verify the availability of something by

*executing* a program, which, by definition, cannot work in

cross-compilation mode).

This works just fine when the target architecture is ARM or PowerPC

and the build machine is x86 or x86_64. Unfortunately, when the target

architecture is x86_64 and the build machine is also x86_64, the

cross-compilation mode detection concludes that we are not

cross-compiling, because it succeeds in running this small program.

However, while it succeeds in running this basic small program, some

other programs executed later through AC_TRY_RUN tests do not work,

because they have target library dependencies that are not available

on the build machine. For example, the libxml2 test fails to *run*

because libxml2 is not available on the build machine, only in the

target/staging directories. So trying to run a program linked against

libxml2, on the build machine, simply doesn't make sense.

We fix this problem by just forcing PHP to think that we're

cross-compiling (which is always the case with Buildroot, as we're at

the moment never building PHP for the host). Unfortunately, the

configure.in file dates back from the autoconf 2.13 era, so the

configure script does not understand the ac_cv_prog_cc_cross cache

variable, and we cannot easily regenerate the configure script using

our package autoconf version. The easiest solution is therefore to

simply patch the configure script to make the cross-compilation test

fail: we replace the execution of the program by a call to false,

which always fail, leading the configure script to understand that we

*are* cross-compiling.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Index: b/configure

===================================================================

--- a/configure

+++ b/configure

@@ -2387,7 +2387,7 @@

 if { (eval echo configure:2388: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext}; then

   ac_cv_prog_cc_works=yes

   # If we can't run a trivial program, we are probably using a cross compiler.

-  if (./conftest; exit) 2>/dev/null; then

+  if (false; exit) 2>/dev/null; then

     ac_cv_prog_cc_cross=no

   else

     ac_cv_prog_cc_cross=yes