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

[Adhemerval Zanella Netto]

On 28/10/25 17:28, H.J. Lu wrote:
> On Wed, Oct 29, 2025 at 1:13 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>> 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
> 
> This change doesn't match the subject which should require clang 18 or above.

But this does make clang 17 older fail.  On aarch64:

checking if [...]/clang+llvm-17.0.6-aarch64-linux-gnu/bin/clang -target aarch64-linux-gnu  is sufficient to build libc... no
checking for python3... python3
checking version of python3... 3.12.3, ok
configure: error:
*** These critical programs are missing or too old: 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);
> 
> This should be a separate patch with a clear explanation.

Fair enough, I will move this a different patch.