diff mbox series

ldbl-opt: Fix -mlong-double-128 configure test for Clang

Message ID 20260726042738.2629285-1-mattst88@gmail.com (mailing list archive)
State Committed
Commit e7a14f03b8d5e34e8ac46db6c377da5c66a3ec2a
Headers
Series ldbl-opt: Fix -mlong-double-128 configure test for Clang |

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Commit Message

Matt Turner July 26, 2026, 4:27 a.m. UTC 
  The check for -mlong-double-128 support wrapped its test code in
AC_LANG_PROGRAM, which places the body inside main().  The body defines
a function, so it became a nested function definition -- a GCC extension
that Clang does not implement, making the test fail (and thus the whole
build error out) with Clang even though it supports -mlong-double-128.

Use AC_LANG_SOURCE so the function is defined at file scope, matching the
pattern already used by the powerpc64le compiler checks, and regenerate
configure.
---
 sysdeps/ieee754/ldbl-opt/configure    | 7 -------
 sysdeps/ieee754/ldbl-opt/configure.ac | 2 +-
 2 files changed, 1 insertion(+), 8 deletions(-)
 mode change 100644 => 100755 sysdeps/ieee754/ldbl-opt/configure

Comments

Sam James July 26, 2026, 2:11 p.m. UTC | #1 
Matt Turner <mattst88@gmail.com> writes:

> The check for -mlong-double-128 support wrapped its test code in
> AC_LANG_PROGRAM, which places the body inside main().  The body defines
> a function, so it became a nested function definition -- a GCC extension
> that Clang does not implement, making the test fail (and thus the whole
> build error out) with Clang even though it supports -mlong-double-128.

Good catch!

>
> Use AC_LANG_SOURCE so the function is defined at file scope, matching the
> pattern already used by the powerpc64le compiler checks, and regenerate
> configure.

Looks like sysdeps/unix/sysv/linux/powerpc/configure.ac has the same
problem.

> ---
>  sysdeps/ieee754/ldbl-opt/configure    | 7 -------
>  sysdeps/ieee754/ldbl-opt/configure.ac | 2 +-
>  2 files changed, 1 insertion(+), 8 deletions(-)
>  mode change 100644 => 100755 sysdeps/ieee754/ldbl-opt/configure
>
> diff --git ./sysdeps/ieee754/ldbl-opt/configure ./sysdeps/ieee754/ldbl-opt/configure
> old mode 100644
> new mode 100755
> index bc6552da0b..7769cc9781
> --- ./sysdeps/ieee754/ldbl-opt/configure
> +++ ./sysdeps/ieee754/ldbl-opt/configure
> @@ -13,17 +13,10 @@ CFLAGS="$CFLAGS -mlong-double-128"
>  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
>  /* end confdefs.h.  */
>  
> -int
> -main (void)
> -{
> -
>  #ifndef __LONG_DOUBLE_128__
>  # error "compiler did not predefine __LONG_DOUBLE_128__ as expected"
>  #endif
>  long double foobar (long double x) { return x; }
> -  ;
> -  return 0;
> -}
>  _ACEOF
>  if ac_fn_c_try_compile "$LINENO"
>  then :
> diff --git ./sysdeps/ieee754/ldbl-opt/configure.ac ./sysdeps/ieee754/ldbl-opt/configure.ac
> index 70e3b32dc6..1c500ad581 100644
> --- ./sysdeps/ieee754/ldbl-opt/configure.ac
> +++ ./sysdeps/ieee754/ldbl-opt/configure.ac
> @@ -6,7 +6,7 @@ AC_CACHE_CHECK(whether $CC $CFLAGS supports -mlong-double-128,
>  	       libc_cv_mlong_double_128, [dnl
>  save_CFLAGS="$CFLAGS"
>  CFLAGS="$CFLAGS -mlong-double-128"
> -AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[
> +AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
>  #ifndef __LONG_DOUBLE_128__
>  # error "compiler did not predefine __LONG_DOUBLE_128__ as expected"
>  #endif
Matt Turner July 26, 2026, 6:43 p.m. UTC | #2 
On Sun, Jul 26, 2026 at 10:11 AM Sam James <sam@gentoo.org> wrote:
>
> Matt Turner <mattst88@gmail.com> writes:
>
> > The check for -mlong-double-128 support wrapped its test code in
> > AC_LANG_PROGRAM, which places the body inside main().  The body defines
> > a function, so it became a nested function definition -- a GCC extension
> > that Clang does not implement, making the test fail (and thus the whole
> > build error out) with Clang even though it supports -mlong-double-128.
>
> Good catch!
>
> >
> > Use AC_LANG_SOURCE so the function is defined at file scope, matching the
> > pattern already used by the powerpc64le compiler checks, and regenerate
> > configure.
>
> Looks like sysdeps/unix/sysv/linux/powerpc/configure.ac has the same
> problem.

I've sent another patch for that:

Subject: [PATCH] powerpc: Fix -mlong-double-128 IBM format configure
test for Clang
Sam James Aug. 6, 2026, 10:11 p.m. UTC | #3 
Matt Turner <mattst88@gmail.com> writes:

> The check for -mlong-double-128 support wrapped its test code in
> AC_LANG_PROGRAM, which places the body inside main().  The body defines
> a function, so it became a nested function definition -- a GCC extension
> that Clang does not implement, making the test fail (and thus the whole
> build error out) with Clang even though it supports -mlong-double-128.
>
> Use AC_LANG_SOURCE so the function is defined at file scope, matching the
> pattern already used by the powerpc64le compiler checks, and regenerate
> configure.

Reviewed-by: Sam James <sam@gentoo.org>

> ---
>  sysdeps/ieee754/ldbl-opt/configure    | 7 -------
>  sysdeps/ieee754/ldbl-opt/configure.ac | 2 +-
>  2 files changed, 1 insertion(+), 8 deletions(-)
>  mode change 100644 => 100755 sysdeps/ieee754/ldbl-opt/configure
>
> diff --git ./sysdeps/ieee754/ldbl-opt/configure ./sysdeps/ieee754/ldbl-opt/configure
> old mode 100644
> new mode 100755
> index bc6552da0b..7769cc9781
> --- ./sysdeps/ieee754/ldbl-opt/configure
> +++ ./sysdeps/ieee754/ldbl-opt/configure
> @@ -13,17 +13,10 @@ CFLAGS="$CFLAGS -mlong-double-128"
>  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
>  /* end confdefs.h.  */
>  
> -int
> -main (void)
> -{
> -
>  #ifndef __LONG_DOUBLE_128__
>  # error "compiler did not predefine __LONG_DOUBLE_128__ as expected"
>  #endif
>  long double foobar (long double x) { return x; }
> -  ;
> -  return 0;
> -}
>  _ACEOF
>  if ac_fn_c_try_compile "$LINENO"
>  then :
> diff --git ./sysdeps/ieee754/ldbl-opt/configure.ac ./sysdeps/ieee754/ldbl-opt/configure.ac
> index 70e3b32dc6..1c500ad581 100644
> --- ./sysdeps/ieee754/ldbl-opt/configure.ac
> +++ ./sysdeps/ieee754/ldbl-opt/configure.ac
> @@ -6,7 +6,7 @@ AC_CACHE_CHECK(whether $CC $CFLAGS supports -mlong-double-128,
>  	       libc_cv_mlong_double_128, [dnl
>  save_CFLAGS="$CFLAGS"
>  CFLAGS="$CFLAGS -mlong-double-128"
> -AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[
> +AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
>  #ifndef __LONG_DOUBLE_128__
>  # error "compiler did not predefine __LONG_DOUBLE_128__ as expected"
>  #endif
diff mbox series

Patch

diff --git ./sysdeps/ieee754/ldbl-opt/configure ./sysdeps/ieee754/ldbl-opt/configure
old mode 100644
new mode 100755
index bc6552da0b..7769cc9781
--- ./sysdeps/ieee754/ldbl-opt/configure
+++ ./sysdeps/ieee754/ldbl-opt/configure
@@ -13,17 +13,10 @@  CFLAGS="$CFLAGS -mlong-double-128"
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
-int
-main (void)
-{
-
 #ifndef __LONG_DOUBLE_128__
 # error "compiler did not predefine __LONG_DOUBLE_128__ as expected"
 #endif
 long double foobar (long double x) { return x; }
-  ;
-  return 0;
-}
 _ACEOF
 if ac_fn_c_try_compile "$LINENO"
 then :
diff --git ./sysdeps/ieee754/ldbl-opt/configure.ac ./sysdeps/ieee754/ldbl-opt/configure.ac
index 70e3b32dc6..1c500ad581 100644
--- ./sysdeps/ieee754/ldbl-opt/configure.ac
+++ ./sysdeps/ieee754/ldbl-opt/configure.ac
@@ -6,7 +6,7 @@  AC_CACHE_CHECK(whether $CC $CFLAGS supports -mlong-double-128,
 	       libc_cv_mlong_double_128, [dnl
 save_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS -mlong-double-128"
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 #ifndef __LONG_DOUBLE_128__
 # error "compiler did not predefine __LONG_DOUBLE_128__ as expected"
 #endif