Re: [WIP] glibc: Use /lib/ld-linux-armhf.so.3 for ARM's -mfloat-abi=hard ABI.

[Khem Raj <raj dot khem at gmail dot com>]

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On 04/26/2012 03:03 PM, Joseph S. Myers wrote:
> On Thu, 26 Apr 2012, Carlos O'Donell wrote:
> 
>> (b) Detect dynamic linker used by compiler.
>> 
>> The following new configure test detects the dynamic linker used
>> by the compiler given the current set of options. We store the
>> result in libc_cv_compiler_dynlinker_default for later use in
>> ARM's preconfigure.
> 
> This is far too complicated.  GCC isn't detecting what dynamic
> linker glibc has, after all.  We should simply test if the compiler
> predefines __ARM_PCS_VFP, which is easy to do in the ARM
> preconfigure.
> 
>> I caught a couple of problems early and fixed them though, like
>> not using AC_MSG_ERROR for the configure failure cases because
>> you might be installing headers and not have a compiler capable
>> of compiling an application yet. This does imply that you *might*
>> not get the right set of headers if such headers changed
>> depending on the dynamic linker selected (which they shouldn't).
>> 
>> Comments?
> 
> It shouldn't (ideally) be necessary to configure glibc, or GCC,
> more than once when bootstrapping.  See Roland's comments at 
> <http://sourceware.org/ml/libc-alpha/2012-03/msg00960.html>.  That
> means we don't want any configure tests that will give the wrong
> results in a bootstrap configuration (where you don't have a
> preexisting libc so can't link things using it) - where there are
> existing tests we should remove them, and we should avoid adding
> more.
> 
> Testing preprocessor defines is safe.  Linking without -nostdlib
> isn't safe in configure tests.  While it looks like GCC will still
> pass the default -dynamic-linker option to ld when using -nostdlib,
> I don't think you should really rely on that either.
> 

I have the following patch which is based on Carlos's work and
Joseph's suggestion

Thanks

- -Khem

glibc-2.15

2012-04-30  Carlos O'Donell  <carlos_odonell@mentor.com>
	    Khem Raj <raj.khem@gmail.com>

	* sysdeps/arm/preconfigure: Select armhf based on __ARM_PCS_VFP
	compiler predefine.
	* sysdeps/arm/eabi/armhf/shlib-versions: New file.
	* sysdeps/arm/eabi/armhf/armv6t2/Implies: New file.
	* sysdeps/arm/eabi/armhf/armv7/Implies: New file.



glibc-trunk


2012-04-30  Carlos O'Donell  <carlos_odonell@mentor.com>
	    Khem Raj <raj.khem@gmail.com>

	* sysdeps/arm/preconfigure: Select armhf based on __ARM_PCS_VFP
	compiler predefine.
	* sysdeps/arm/armhf/shlib-versions: New file.
	* sysdeps/arm/armhf/armv6t2/Implies: New file.
	* sysdeps/arm/armhf/armv7/Implies: New file.



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Index: libc/ports/sysdeps/arm/eabi/armhf/armv6t2/Implies
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ libc/ports/sysdeps/arm/eabi/armhf/armv6t2/Implies	2012-04-30 20:27:01.788730633 -0700
@@ -0,0 +1 @@
+arm/eabi/armv6t2
Index: libc/ports/sysdeps/arm/eabi/armhf/armv7/Implies
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ libc/ports/sysdeps/arm/eabi/armhf/armv7/Implies	2012-04-30 20:26:37.332729450 -0700
@@ -0,0 +1 @@
+arm/eabi/armv7
Index: libc/ports/sysdeps/arm/eabi/armhf/shlib-versions
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ libc/ports/sysdeps/arm/eabi/armhf/shlib-versions	2012-04-30 20:28:01.764733536 -0700
@@ -0,0 +1,6 @@
+# As of 2.16 the -mfloat-abi=hard ABI variant has a new unique
+# name for the dynamic loader.
+arm.*-.*-linux-gnueabi.*	DEFAULT			GLIBC_2.4
+
+arm.*-.*-linux-gnueabi.*	ld=ld-linux-armhf.so.3
+
Index: libc/ports/sysdeps/arm/preconfigure
===================================================================
--- libc.orig/ports/sysdeps/arm/preconfigure	2012-04-30 20:23:20.032719900 -0700
+++ libc/ports/sysdeps/arm/preconfigure	2012-04-30 20:24:34.948723526 -0700
@@ -35,6 +35,19 @@
 		  ;;
 		esac
 
+		archcppflag=`echo "" |
+		$CC $CFLAGS $CPPFLAGS -E -dM - |
+		  grep __ARM_PCS_VFP |
+		  sed -e 's/^#define //' -e 's/ .*//'`
+		case x$archcppflag in
+		x__ARM_PCS_VFP)
+		  echo "Found compiler is configured for ARM hard-float ABI"
+		  machine=armhf/$machine
+		  ;;
+		*)
+		  ;;
+		esac
+
 		machine=arm/eabi/$machine
 		if [ "${CFLAGS+set}" != "set" ]; then
 		  CFLAGS="-g -O2"

Index: arm/armhf/armv7/Implies
===================================================================
--- arm/armhf/armv7/Implies	(revision 0)
+++ arm/armhf/armv7/Implies	(revision 0)
@@ -0,0 +1 @@
+arm/armv7
Index: arm/armhf/armv6t2/Implies
===================================================================
--- arm/armhf/armv6t2/Implies	(revision 0)
+++ arm/armhf/armv6t2/Implies	(revision 0)
@@ -0,0 +1 @@
+arm/armv6t2
Index: arm/armhf/shlib-versions
===================================================================
--- arm/armhf/shlib-versions	(revision 0)
+++ arm/armhf/shlib-versions	(revision 0)
@@ -0,0 +1,6 @@
+# As of 2.16 the -mfloat-abi=hard ABI variant has a new unique
+# name for the dynamic loader.
+arm.*-.*-linux-gnueabi.*	DEFAULT			GLIBC_2.4
+
+arm.*-.*-linux-gnueabi.*	ld=ld-linux-armhf.so.3
+
Index: arm/preconfigure
===================================================================
--- arm/preconfigure	(revision 18306)
+++ arm/preconfigure	(working copy)
@@ -34,7 +34,18 @@
 		  echo 2>&1 "arm/preconfigure: Did not find ARM architecture type; using default"
 		  ;;
 		esac
-
+		archcppflag=`echo "" |
+		$CC $CFLAGS $CPPFLAGS -E -dM - |
+		  grep __ARM_PCS_VFP |
+		  sed -e 's/^#define //' -e 's/ .*//'`
+		case x$archcppflag in
+		x__ARM_PCS_VFP)
+		  echo "Found compiler is configured for ARM hard-float ABI"
+		  machine=armhf/$machine
+		  ;;
+		*)
+		  ;;
+		esac
 		machine=arm/$machine
 		if [ "${CFLAGS+set}" != "set" ]; then
 		  CFLAGS="-g -O2"