AC_PROG_CC: try -qlanglvl=extc1x, for IBM XL C V12.1

* lib/autoconf/c.m4 (_AC_PROG_CC_C11): Add -qlanglvl=extc1x, for
IBM XL C V12.1.  It shouldn't pass the C11 test yet, since it's not
documented to support _Alignas, _Alignof, UTF-8 string literals,
and duplicate typedefs, but presumably it will eventually.

diff --git a/lib/autoconf/c.m4 b/lib/autoconf/c.m4
index 808c1045caeb13e8b5bd4cbf6f566c514a92809e..0309416e9d8145c058d8d6c742f38ef964e99261 100644 (file)
--- a/lib/autoconf/c.m4
+++ b/lib/autoconf/c.m4
@@ -1347,7 +1347,7 @@ AC_DEFUN([_AC_PROG_CC_C99],
 [_AC_C_C99_TEST_BODY],
 dnl Try
 dnl GCC                -std=gnu99 (unused restrictive modes: -std=c99 -std=iso9899:1999)
-dnl AIX                -qlanglvl=extc99 (unused restrictive mode: -qlanglvl=stdc99)
+dnl IBM XL C   -qlanglvl=extc99 (unused restrictive mode: -qlanglvl=stdc99)
 dnl HP cc      -AC99
 dnl Intel ICC  -std=c99, -c99 (deprecated)
 dnl IRIX       -c99
@@ -1432,8 +1432,9 @@ struct anonymous
 ]],
 dnl Try
 dnl GCC                -std=gnu11 (unused restrictive mode: -std=c11)
+dnl IBM XL C   -qlanglvl=extc1x (no extc11 or (unused) stdc11 in V12.1)
 dnl with extended modes being tried first.
-[[-std=gnu11]], [$1], [$2])[]dnl
+[[-std=gnu11 -qlanglvl=extc1x]], [$1], [$2])[]dnl
 ])# _AC_PROG_CC_C11
 
 
@@ -1740,7 +1741,7 @@ AC_DEFUN([AC_C_CONST],
   /* NEC SVR4.0.2 mips cc rejects this.  */
   struct point {int x, y;};
   static struct point const zero = {0,0};
-  /* AIX XL C 1.02.0.0 rejects this.
+  /* IBM XL C 1.02.0.0 rejects this.
      It does not let you subtract one const X* pointer from another in
      an arm of an if-expression whose if-part is not a constant
      expression */
@@ -1768,7 +1769,7 @@ AC_DEFUN([AC_C_CONST],
     iptr p = 0;
     ++p;
   }
-  { /* AIX XL C 1.02.0.0 rejects this sort of thing, saying
+  { /* IBM XL C 1.02.0.0 rejects this sort of thing, saying
        "k.c", line 2.27: 1506-025 (S) Operand must be a modifiable lvalue. */
     struct s { int j; const int *ap[3]; } bx;
     struct s *b = &bx; b->j = 5;
@@ -2064,7 +2065,7 @@ AC_DEFUN([AC_OPENMP],
          dnl   Intel C              -openmp
          dnl   SGI C, PGI C         -mp
          dnl   Tru64 Compaq C       -omp
-         dnl   IBM C (AIX, Linux)   -qsmp=omp
+         dnl   IBM XL C (AIX, Linux) -qsmp=omp
           dnl   Cray CCE             -homp
           dnl   NEC SX               -Popenmp
           dnl   Lahey Fortran (Linux)  --openmp