x86: Assume --enable-cet if GCC defaults to CET [BZ #25225]

This links in CET support if GCC defaults to CET.  Otherwise, __CET__
is defined, yet CET functionality is not compiled and linked into the
dynamic loader, resulting in a linker failure due to undefined
references to _dl_cet_check and _dl_open_check.

diff --git a/configure b/configure
index 2f44b66656e74ea571c47293f9af88df271bf7e4..b959d2d9885e53e6adcd7037f8382720555abd40 100755 (executable)
--- a/configure
+++ b/configure
@@ -3777,11 +3777,32 @@ else
 fi
 
 
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+#ifndef __CET__
+#error no CET compiler support
+#endif
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  libc_cv_compiler_default_cet=yes
+else
+  libc_cv_compiler_default_cet=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
 # Check whether --enable-cet was given.
 if test "${enable_cet+set}" = set; then :
   enableval=$enable_cet; enable_cet=$enableval
 else
-  enable_cet=no
+  enable_cet=$libc_cv_compiler_default_cet
 fi
 
 

diff --git a/configure.ac b/configure.ac
index e69c88c543521923e3af9b25b85af2edbb6dc162..49b900c1ed68fa4dd1dadca809ceb6e8b237a89c 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -473,11 +473,18 @@ AC_ARG_ENABLE([mathvec],
              [build_mathvec=$enableval],
              [build_mathvec=notset])
 
+AC_TRY_COMPILE([], [
+#ifndef __CET__
+# error no CET compiler support
+#endif],
+              [libc_cv_compiler_default_cet=yes],
+              [libc_cv_compiler_default_cet=no])
+
 AC_ARG_ENABLE([cet],
              AC_HELP_STRING([--enable-cet],
                             [enable Intel Control-flow Enforcement Technology (CET), x86 only]),
              [enable_cet=$enableval],
-             [enable_cet=no])
+             [enable_cet=$libc_cv_compiler_default_cet])
 
 # We keep the original values in `$config_*' and never modify them, so we
 # can write them unchanged into config.make.  Everything else uses