Patchwork Fix libgfortran cross compile configury w.r.t newlib

login
register
mail settings
Submitter Marcus Shawcroft
Date Sept. 26, 2013, 1:47 p.m.
Message ID <52443AFE.5050802@arm.com>
Download mbox | patch
Permalink /patch/278198/
State New
Headers show

Comments

Marcus Shawcroft - Sept. 26, 2013, 1:47 p.m.
This patch:

http://gcc.gnu.org/ml/fortran/2013-06/msg00038.html

... breaks libgfortran configure against newlib.

The solution implemented hard wires an assumption in 
libgfortran/configure.ac that newlib provides strtold().  This 
assumption is not correct, newlib only provides an implementation of 
strtold on systems where sizeof(long double) == sizeof(double).  This 
manifests as a regression when trying to build a cross aarch64 bare 
metal toolchain with fortran enabled.

The attached patch tightens the condition introduced in the earlier 
patch such that we continue to call AC_CHECK_FUNCS_ONCE unless we know 
that link tests are not possible, in which case we fall back to the 
existing broken assumption.

I'm in two minds about whether further sticky tape of this form is the 
right approach or whether the original patch should be reverted until a 
proper fix that does not regress the tree can be found.

Thoughts?

2013-09-26  Marcus Shawcroft  <marcus.shawcroft@arm.com>

         * configure.ac (AC_CHECK_FUNCS_ONCE): Make if statement
         dependent on gcc_no_link.

Cheers
/Marcus
Steve Ellcey - Sept. 26, 2013, 3:17 p.m.
On Thu, 2013-09-26 at 14:47 +0100, Marcus Shawcroft wrote:

> I'm in two minds about whether further sticky tape of this form is the 
> right approach or whether the original patch should be reverted until a 
> proper fix that does not regress the tree can be found.
> 
> Thoughts?
> 
> 2013-09-26  Marcus Shawcroft  <marcus.shawcroft@arm.com>
> 
>          * configure.ac (AC_CHECK_FUNCS_ONCE): Make if statement
>          dependent on gcc_no_link.
> 
> Cheers
> /Marcus

I think this patch is a good fix.  I (obviously) don't favor reverting
the previous patch because that would re-break the Fortran build on MIPS
bare-metal cross compilers (or any compiler where a linker script is
needed).  Any 'proper' fix should address libstdc++, libjava, and other
libraries as well as libgfortran and I don't know what a cleaner fix
would be.  In fact I would say the other libraries should consider using
this fix.  The only reason they don't run into this problem too is that
they don't depend on any long double functions or any other functions
that are optionally built by newlib.

I will test this patch on my targets and make sure it works for me, but
I don't see why it would not.

Steve Ellcey
sellcey@mips.com
Steve Ellcey - Sept. 27, 2013, 4:08 p.m.
On Thu, 2013-09-26 at 14:47 +0100, Marcus Shawcroft wrote:

> I'm in two minds about whether further sticky tape of this form is the 
> right approach or whether the original patch should be reverted until a 
> proper fix that does not regress the tree can be found.
> 
> Thoughts?
> 
> 2013-09-26  Marcus Shawcroft  <marcus.shawcroft@arm.com>
> 
>          * configure.ac (AC_CHECK_FUNCS_ONCE): Make if statement
>          dependent on gcc_no_link.
> 
> Cheers
> /Marcus

Well, I thought this patch would work for me, but it does not.  It looks
like gcc_no_link is set to 'no' on my target because, technically, I can
link even if I don't use a linker script.  I just can't find any
functions.


% cat x.c
int main (void) { return 0; }
% mips-mti-elf-gcc x.c -o x
/local/home/sellcey/nightly/install-mips-mti-elf/lib/gcc/mips-mti-elf/4.9.0/../../../../mips-mti-elf/bin/ld: warning: cannot find entry symbol __start; defaulting to 0000000000400098
% echo $?
0


% cat y.c
int main (void) { exit (0); }
% install-mips-mti-elf/bin/mips-mti-elf-gcc y.c -o y
/local/home/sellcey/nightly/install-mips-mti-elf/lib/gcc/mips-mti-elf/4.9.0/../../../../mips-mti-elf/bin/ld: warning: cannot find entry symbol __start; defaulting to 0000000000400098
/tmp/ccdG78PN.o: In function `main':
y.c:(.text+0x14): undefined reference to `exit'
collect2: error: ld returned 1 exit status
ubuntu-sellcey % echo $?
1


Steve Ellcey
sellcey@mips.com
Marcus Shawcroft - Sept. 30, 2013, 12:40 p.m.
On 27/09/13 17:08, Steve Ellcey wrote:
> On Thu, 2013-09-26 at 14:47 +0100, Marcus Shawcroft wrote:
>
>> I'm in two minds about whether further sticky tape of this form is the
>> right approach or whether the original patch should be reverted until a
>> proper fix that does not regress the tree can be found.
>>
>> Thoughts?
>>
>> 2013-09-26  Marcus Shawcroft  <marcus.shawcroft@arm.com>
>>
>>           * configure.ac (AC_CHECK_FUNCS_ONCE): Make if statement
>>           dependent on gcc_no_link.
>>
>> Cheers
>> /Marcus
>
> Well, I thought this patch would work for me, but it does not.  It looks
> like gcc_no_link is set to 'no' on my target because, technically, I can
> link even if I don't use a linker script.  I just can't find any
> functions.
>
>
> % cat x.c
> int main (void) { return 0; }
> % mips-mti-elf-gcc x.c -o x
> /local/home/sellcey/nightly/install-mips-mti-elf/lib/gcc/mips-mti-elf/4.9.0/../../../../mips-mti-elf/bin/ld: warning: cannot find entry symbol __start; defaulting to 0000000000400098
> % echo $?
> 0
>
>
> % cat y.c
> int main (void) { exit (0); }
> % install-mips-mti-elf/bin/mips-mti-elf-gcc y.c -o y
> /local/home/sellcey/nightly/install-mips-mti-elf/lib/gcc/mips-mti-elf/4.9.0/../../../../mips-mti-elf/bin/ld: warning: cannot find entry symbol __start; defaulting to 0000000000400098
> /tmp/ccdG78PN.o: In function `main':
> y.c:(.text+0x14): undefined reference to `exit'
> collect2: error: ld returned 1 exit status
> ubuntu-sellcey % echo $?
> 1

In which case gating on gcc_no_link could be replaced with a test that 
looks to see if we can link with the library.  Perhaps looking for 
exit() or some such that might reasonably be expected to be present.

For example:

AC_CHECK_FUNC(exit)
if test "x${with_newlib}" = "xyes" -a "x${ac_cv_func_exit}" = "xno"; then

/Marcus

Patch

diff --git a/libgfortran/configure.ac b/libgfortran/configure.ac
index 4609eba..411ab38 100644
--- a/libgfortran/configure.ac
+++ b/libgfortran/configure.ac
@@ -261,7 +261,7 @@  GCC_HEADER_STDINT(gstdint.h)
 AC_CHECK_MEMBERS([struct stat.st_blksize, struct stat.st_blocks, struct stat.st_rdev])
 
 # Check for library functions.
-if test "x${with_newlib}" = "xyes"; then
+if test "x${with_newlib}" = "xyes" -a "x${gcc_no_link}" = "xyes" ; then
    # We are being configured with a cross compiler.  AC_REPLACE_FUNCS
    # may not work correctly, because the compiler may not be able to
    # link executables.