configure: go back to platform-based EXTERN_PREFIX test

Commit 6ad1f58 (svn r28151) changed EXTERN_PREFIX detection to use
a "general" configure test instead of determining it based on
platform. However, this "general" test depends on assumptions about
object file contents, and actually fails if compiling with gcc -flto
for example. Go back to the simple platform-based test. Leave out the
OS2 (no longer supported) and OpenBSD !ELF (no idea what that is, but
probably not something I'd care about supporting) parts from the old
test.

Remove configure switch --nm, as it was only used for the hacky
EXTERN_PREFIX test.

Simply disable the use of EXTERN_ASM (same as EXTERN_PREFIX under
another name) in wrapper.S; this seems to have been added for OS/2
only, and the file should not get compiled on any platform with a
nonempty prefix now.

Author: Uoti Urpala

configure

@@ -424,7 +424,6 @@ Miscellaneous options:
   --enable-runtime-cpudetection    enable runtime CPU detection [disable]
   --enable-cross-compile enable cross-compilation [disable]
   --cc=COMPILER          C compiler to build MPlayer [gcc]
-  --nm=NM                nm tool to build MPlayer [nm]
   --pkg-config=PKGCONFIG pkg-config to find some libraries [pkg-config]
   --windres=WINDRES      windres to build MPlayer [windres]
   --target=PLATFORM      target platform (i386-linux, arm-linux, etc)
@@ -498,7 +497,6 @@ _windres=auto
 _cc=auto
 test "$CC" && _cc="$CC"
 _as=auto
-_nm=auto
 _runtime_cpudetection=no
 _cross_compile=no
 _prefix="/usr/local"
@@ -687,9 +685,6 @@ for ac_option do
   --cc=*)
     _cc=$(echo $ac_option | cut -d '=' -f 2)
     ;;
-  --nm=*)
-    _nm=$(echo $ac_option | cut -d '=' -f 2)
-    ;;
   --pkg-config=*)
     _pkg_config=$(echo $ac_option | cut -d '=' -f 2)
     ;;
@@ -1298,11 +1293,6 @@ echo "Detected host architecture: $host_arch"
 
 # ---
 
-if test "$_nm" = auto ; then
-  _nm=$($_cc -print-prog-name=nm)
-  test -z "$_nm" && _nm=nm
-fi
-
 # XXX: this should be ok..
 _cpuinfo="echo"
 
@@ -2033,18 +2023,6 @@ fi
 echores "$_byte_order"
 
 
-echocheck "extern symbol prefix"
-cat > $TMPC << EOF
-int ff_extern;
-EOF
-cc_check -c || die "Symbol mangling check failed."
-sym=$($_nm -P -g $TMPEXE)
-extern_prefix=${sym%%ff_extern*}
-def_extern_asm="#define EXTERN_ASM $extern_prefix"
-def_extern_prefix="#define EXTERN_PREFIX \"$extern_prefix\""
-echores $extern_prefix
-
-
 echocheck "assembler support of -pipe option"
 # -I. helps to detect compilers that just misunderstand -pipe like Sun C
 cflag_check -pipe -I. && _pipe="-pipe" && echores "yes" || echores "no"

loader/wrapper.S

@@ -2,6 +2,7 @@
 
 #define GLUE(a, b) a ## b
 #define JOIN(a, b) GLUE(a, b)
+#define EXTERN_ASM
 #define MANGLE(s)  JOIN(EXTERN_ASM, s)
 
 .data

mangle.h

@@ -31,6 +31,12 @@
 #define attribute_used
 #endif
 
+#if defined(_WIN32) || defined(__APPLE__)
+#define EXTERN_PREFIX "_"
+#else
+#define EXTERN_PREFIX ""
+#endif
+
 #if ARCH_X86_64 && defined(PIC)
 #define MANGLE(a) EXTERN_PREFIX #a "(%%rip)"
 #else