[glibc/azanella/clang] configure: Use -Wno-ignored-attributes if compiler warns about multiple aliases

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b6694a1f8b228fa5e66c9e0207381adbfa8425af

commit b6694a1f8b228fa5e66c9e0207381adbfa8425af
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Fri Mar 11 10:40:44 2022 -0300

    configure: Use -Wno-ignored-attributes if compiler warns about multiple aliases
    
    clang emits an warning when a double alias redirection is used, to warn
    the the original symbol will be used even when weak definition is
    overridden.  Howerver, this is a common pattern for weak_alias, where
    multiple alias are set to same symbol.

Diff:
---
 configure                             | 30 ++++++++++++++++++++++++++++++
 configure.ac                          | 22 ++++++++++++++++++++++
 math/Makefile                         |  8 ++++++++
 sysdeps/x86_64/fpu/multiarch/Makefile |  2 ++
 4 files changed, 62 insertions(+)

diff --git a/configure b/configure
index 57181a386c..3b1371b189 100755
--- a/configure
+++ b/configure
@@ -7194,6 +7194,36 @@ printf "%s\n" "$libc_cv_wno_ignored_attributes" >&6; }
 config_vars="$config_vars
 config-cflags-wno-ignored-attributes = $libc_cv_wno_ignored_attributes"
 
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if -Wno-ignored-attributes is required for aliases" >&5
+printf %s "checking if -Wno-ignored-attributes is required for aliases... " >&6; }
+if test ${libc_cv_wno_ignored_attributes+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  cat > conftest.c <<EOF
+void __foo (void)
+{
+}
+extern __typeof (__foo) foo __attribute__ ((weak, alias ("__foo")));
+extern __typeof (__foo) bar __attribute__ ((weak, alias ("foo")));
+EOF
+libc_cv_wno_ignored_attributes=""
+if ! { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -Werror -c conftest.c'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then
+  libc_cv_wno_ignored_attributes="-Wno-ignored-attributes"
+fi
+rm -f conftest*
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_wno_ignored_attributes" >&5
+printf "%s\n" "$libc_cv_wno_ignored_attributes" >&6; }
+config_vars="$config_vars
+config-cflags-wno-ignored-attributes = $libc_cv_wno_ignored_attributes"
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether cc puts quotes around section names" >&5
 printf %s "checking whether cc puts quotes around section names... " >&6; }
 if test ${libc_cv_have_section_quotes+y}
diff --git a/configure.ac b/configure.ac
index b0fc9c2766..1f31d967ab 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1394,6 +1394,28 @@ rm -f conftest*])
 LIBC_CONFIG_VAR([config-cflags-wno-ignored-attributes],
 		[$libc_cv_wno_ignored_attributes])
 
+dnl clang emits an warning when a double alias redirection is used, to warn
+dnl the the original symbol will be used even when weak definition is overridden.
+dnl This is a common pattern for weak_alias, where multiple alias are set to
+dnl same symbol.
+AC_CACHE_CHECK([if -Wno-ignored-attributes is required for aliases],
+	       libc_cv_wno_ignored_attributes, [dnl
+cat > conftest.c <<EOF
+void __foo (void)
+{
+}
+extern __typeof (__foo) foo __attribute__ ((weak, alias ("__foo")));
+extern __typeof (__foo) bar __attribute__ ((weak, alias ("foo")));
+EOF
+libc_cv_wno_ignored_attributes=""
+if ! AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -Werror -c conftest.c])
+then
+  libc_cv_wno_ignored_attributes="-Wno-ignored-attributes"
+fi
+rm -f conftest*])
+LIBC_CONFIG_VAR([config-cflags-wno-ignored-attributes],
+		[$libc_cv_wno_ignored_attributes])
+
 AC_CACHE_CHECK(whether cc puts quotes around section names,
 	       libc_cv_have_section_quotes,
 	       [cat > conftest.c <<EOF
diff --git a/math/Makefile b/math/Makefile
index a9daae09de..bf0393b7a7 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -1002,6 +1002,14 @@ CFLAGS-s_y0f.c += -fno-builtin-y0f32
 CFLAGS-s_y1f.c += -fno-builtin-y1f32
 CFLAGS-s_ynf.c += -fno-builtin-ynf32
 
+CFLAGS-s_fabsf128.c += $(config-cflags-wno-ignored-attributes)
+CFLAGS-fraiseexcpt.c += $(config-cflags-wno-ignored-attributes)
+CFLAGS-fegetround.c += $(config-cflags-wno-ignored-attributes)
+CFLAGS-fesetround.c += $(config-cflags-wno-ignored-attributes)
+CFLAGS-fegetenv.c += $(config-cflags-wno-ignored-attributes)
+CFLAGS-fesetenv.c += $(config-cflags-wno-ignored-attributes)
+CFLAGS-feholdexcpt.c += $(config-cflags-wno-ignored-attributes)
+
 # These files quiet sNaNs in a way that is optimized away without
 # -fsignaling-nans.
 CFLAGS-s_modf.c += $(config-cflags-signaling-nans)
diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile b/sysdeps/x86_64/fpu/multiarch/Makefile
index ea81753b70..0253edf027 100644
--- a/sysdeps/x86_64/fpu/multiarch/Makefile
+++ b/sysdeps/x86_64/fpu/multiarch/Makefile
@@ -44,6 +44,8 @@ libm-sysdep_routines += \
   s_tan-fma \
 # libm-sysdep_routines
 
+CFLAGS-s_sincos.c += $(config-cflags-wno-ignored-attributes)
+
 CFLAGS-e_asin-fma.c = -mfma -mavx2
 CFLAGS-e_atan2-fma.c = -mfma -mavx2
 CFLAGS-e_exp-fma.c = -mfma -mavx2