2 files changed, 58 insertions, 0 deletions
diff --git a/sysdeps/i386/configure b/sysdeps/i386/configure
index d81b613a..a1a0fe7 100644
--- a/sysdeps/i386/configure
+++ b/sysdeps/i386/configure
@@ -32,6 +32,45 @@ $as_echo "$ac_res" >&6; }
 # This file is generated from configure.in by Autoconf.  DO NOT EDIT!
  # Local configure fragment for sysdeps/i386.
 
+# The GNU C Library can't be built for i386.  There are several reasons for
+# this restriction.  The primary reason is that i386 lacks the atomic
+# operations required to support the current NPTL implementation.  While it is
+# possible that such atomic operations could be emulated in the kernel to date
+# no such work has been done to enable this.  Even with NPTL disabled you still
+# have no atomic.h implementation.  Given the declining use of i386 we disable
+# support for building with `-march=i386' or `-mcpu=i386.' We don't explicitly
+# check for i386, instead we make sure the compiler has support for inlining
+# the builtin __sync_val_compare_and_swap. If it does then we should have no
+# problem building for i386.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for compiler support of inlined builtin function __sync_val_compare_and_swap" >&5
+$as_echo_n "checking for compiler support of inlined builtin function __sync_val_compare_and_swap... " >&6; }
+libc_compiler_builtin_inlined=no
+cat > conftest.c <<EOF
+int _start (void) { int a, b, c; __sync_val_compare_and_swap (&a, b, c); return 0; }
+EOF
+if ! { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS
+		     -O0 -nostdlib -nostartfiles
+		     -S conftest.c -o - | fgrep "__sync_val_compare_and_swap"
+		     1>&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then
+  libc_compiler_builtin_inlined=yes
+fi
+rm -f conftest*
+if test $libc_compiler_builtin_inlined = yes; then
+  libc_cv_unsupported_i386=no
+else
+  as_fn_error $? "
+*** Building with -march=i386/-mcpu=i386 is not supported.
+*** Please use host i786, i686, i586, or i486." "$LINENO" 5
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_compiler_builtin_inlined" >&5
+$as_echo "$libc_compiler_builtin_inlined" >&6; }
+
 
 ac_fn_c_check_header_compile "$LINENO" "cpuid.h" "ac_cv_header_cpuid_h" "/* No default includes.  */
 "
diff --git a/sysdeps/i386/configure.in b/sysdeps/i386/configure.in
index 9967a16..56a7c1f 100644
--- a/sysdeps/i386/configure.in
+++ b/sysdeps/i386/configure.in
@@ -1,6 +1,25 @@
 GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
 # Local configure fragment for sysdeps/i386.
 
+# The GNU C Library can't be built for i386.  There are several reasons for
+# this restriction.  The primary reason is that i386 lacks the atomic
+# operations required to support the current NPTL implementation.  While it is
+# possible that such atomic operations could be emulated in the kernel to date
+# no such work has been done to enable this.  Even with NPTL disabled you still
+# have no atomic.h implementation.  Given the declining use of i386 we disable
+# support for building with `-march=i386' or `-mcpu=i386.' We don't explicitly
+# check for i386, instead we make sure the compiler has support for inlining
+# the builtin __sync_val_compare_and_swap. If it does then we should have no
+# problem building for i386.
+LIBC_COMPILER_BUILTIN_INLINED(
+  [__sync_val_compare_and_swap],
+  [int a, b, c; __sync_val_compare_and_swap (&a, b, c);],
+  [-O0],
+  [libc_cv_unsupported_i386=no],
+  [AC_MSG_ERROR([
+*** Building with -march=i386/-mcpu=i386 is not supported.
+*** Please use host i786, i686, i586, or i486.])])
+
 AC_CHECK_HEADER([cpuid.h], ,
   [AC_MSG_ERROR([gcc must provide the <cpuid.h> header])],
   [/* No default includes.  */])