x86: Fix bug about glibc.cpu.hwcaps.

Recorded in [BZ #30183]:

1. export GLIBC_TUNABLES=glibc.cpu.hwcaps=-AVX512
2. Add  _dl_printf("p -- %s\n", p); just before switch(nl) in
   sysdeps/x86/cpu-tunables.c
3. compiled and run ./testrun.sh /usr/bin/ls
you will get:

p -- -AVX512
p -- LC_ADDRESS=en_US.UTF-8
p -- LC_NUMERIC=C
...

The function, TUNABLE_CALLBACK (set_hwcaps)
(tunable_val_t *valp), checks far more than it should and it
should stop at end of "-AVX512".

diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c
index d3e1367..772fb0c 100644 (file)
--- a/sysdeps/x86/cpu-tunables.c
+++ b/sysdeps/x86/cpu-tunables.c
@@ -107,13 +107,13 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
      NOTE: the IFUNC selection may change over time.  Please check all
      multiarch implementations when experimenting.  */
 
-  const char *p = valp->strval;
+  const char *p = valp->strval, *c;
   struct cpu_features *cpu_features = &GLRO(dl_x86_cpu_features);
   size_t len;
 
   do
     {
-      const char *c, *n;
+      const char *n;
       bool disable;
       size_t nl;
 
@@ -283,7 +283,7 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
        }
       p += len + 1;
     }
-  while (*p != '\0');
+  while (*c != '\0');
 }
 
 # if CET_ENABLED