[PATCH v2 27/28] configure: remove overly restrictive check for clang

[Adhemerval Zanella]

The clang support is still experimental and not all testcase build
or run correctly.  Only clang 18 and onwards is supported and only
for x86_64-linux-gnu and aarch64-linux-gnu.
---
 NEWS         | 5 +++++
 configure    | 4 ++--
 configure.ac | 4 ++--
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index 244f7613d8..b4348ac51b 100644
--- a/NEWS
+++ b/NEWS
@@ -13,6 +13,11 @@ Major new features:
 
 * The ISO C23 memalignment function has been added.
 
+* Initial support for building with clang has been added.  It requires
+  at least clang version 18, aarch64-linux-gnu or x86_64-linux-gnu
+  targets, and libgcc compatible runtime (including libgcc_s.so for
+  pthread cancellation and backtrace runtime support).
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * Support for dumped heaps has been removed - malloc_set_state() now always
diff --git a/configure b/configure
index 3c926be3ec..a21ce56302 100755
--- a/configure
+++ b/configure
@@ -5799,7 +5799,7 @@ int
 main (void)
 {
 
-#if !defined __GNUC__ || __GNUC__ < 12 || (__GNUC__ == 12 && __GNUC_MINOR__ < 1)
+#if (!defined __GNUC__ || __GNUC__ < 12 || (__GNUC__ == 12 && __GNUC_MINOR__ < 1)) && (!defined __clang__ || __clang_major__ < 18)
 #error insufficient compiler
 #endif
   ;
@@ -7642,7 +7642,7 @@ else case e in #(
 extern char *strstr (const char *, const char *) __asm ("my_strstr");
 char *foo (const char *a, const char *b)
 {
-  return __builtin_strstr (a, b);
+  return strstr (a, b);
 }
 EOF
 if { ac_try='${CC-cc} -O3 -S conftest.c -o - | grep -F "my_strstr" > /dev/null'
diff --git a/configure.ac b/configure.ac
index 890f1b1c9c..29c45632fd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -585,7 +585,7 @@ AC_CHECK_PROG_VER(BISON, bison, --version,
 # Require GCC 12.1 to build.
 AC_CACHE_CHECK([if $CC is sufficient to build libc], libc_cv_compiler_ok, [
 AC_PREPROC_IFELSE([AC_LANG_PROGRAM([[]], [[
-#if !defined __GNUC__ || __GNUC__ < 12 || (__GNUC__ == 12 && __GNUC_MINOR__ < 1)
+#if (!defined __GNUC__ || __GNUC__ < 12 || (__GNUC__ == 12 && __GNUC_MINOR__ < 1)) && (!defined __clang__ || __clang_major__ < 18)
 #error insufficient compiler
 #endif]])],
 	       [libc_cv_compiler_ok=yes],
@@ -1474,7 +1474,7 @@ cat > conftest.c <<\EOF
 extern char *strstr (const char *, const char *) __asm ("my_strstr");
 char *foo (const char *a, const char *b)
 {
-  return __builtin_strstr (a, b);
+  return strstr (a, b);
 }
 EOF
 dnl
-- 
2.43.0