stdio: Remove UB on printf_fp

The __printf_fp_buffer_1 issues count_leading_zeros with 0 argument,
which might leads to call __builtin_ctz depending of the ABI.
Replace with stdbit.h function instead.

Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Paul Eggert <eggert@cs.ucla.edu>

diff --git a/stdio-common/printf_fp.c b/stdio-common/printf_fp.c
index 5b46ddcaec03e71d1cd8299b16812ada8b2f03e7..0039e1b20b1a2daff6156098a45ce0b1f340f3bd 100644 (file)
--- a/stdio-common/printf_fp.c
+++ b/stdio-common/printf_fp.c
@@ -29,7 +29,6 @@
 #include <gmp.h>
 #include <ieee754.h>
 #include <stdlib/gmp-impl.h>
-#include <stdlib/longlong.h>
 #include <stdlib/fpioconst.h>
 #include <locale/localeinfo.h>
 #include <limits.h>
@@ -40,6 +39,7 @@
 #include <stdlib.h>
 #include <wchar.h>
 #include <stdbool.h>
+#include <stdbit.h>
 #include <rounding-mode.h>
 #include <printf_buffer.h>
 #include <printf_buffer_to_file.h>
@@ -386,7 +386,7 @@ __printf_fp_buffer_1 (struct __printf_buffer *buf, locale_t loc,
                {
                  int cnt;
                  MPN_ASSIGN (p.scale, p.tmp);
-                 count_leading_zeros (cnt, p.scale[p.scalesize - 1]);
+                 cnt = stdc_leading_zeros (p.scale[p.scalesize - 1]);
                  scaleexpo = (p.scalesize - 2) * BITS_PER_MP_LIMB - cnt - 1;
                  exp10 |= 1 << explog;
                }
@@ -408,7 +408,7 @@ __printf_fp_buffer_1 (struct __printf_buffer *buf, locale_t loc,
            ;
 
          /* Determine number of bits the scaling factor is misplaced.  */
-         count_leading_zeros (cnt_h, p.scale[p.scalesize - 1]);
+         cnt_h = stdc_leading_zeros (p.scale[p.scalesize - 1]);
 
          if (cnt_h == 0)
            {
@@ -426,17 +426,17 @@ __printf_fp_buffer_1 (struct __printf_buffer *buf, locale_t loc,
            {
              if (p.scale[i] != 0)
                {
-                 count_trailing_zeros (cnt_l, p.scale[i]);
+                 cnt_l = stdc_trailing_zeros (p.scale[i]);
                  if (p.frac[i] != 0)
                    {
                      int cnt_l2;
-                     count_trailing_zeros (cnt_l2, p.frac[i]);
+                     cnt_l2 = stdc_trailing_zeros (p.frac[i]);
                      if (cnt_l2 < cnt_l)
                        cnt_l = cnt_l2;
                    }
                }
              else
-               count_trailing_zeros (cnt_l, p.frac[i]);
+               cnt_l = stdc_trailing_zeros (p.frac[i]);
 
              /* Now shift the numbers to their optimal position.  */
              if (i == 0 && BITS_PER_MP_LIMB - cnt_h > cnt_l)
@@ -528,7 +528,7 @@ __printf_fp_buffer_1 (struct __printf_buffer *buf, locale_t loc,
              if (cy == 0)
                --p.tmpsize;
 
-             count_leading_zeros (cnt_h, p.tmp[p.tmpsize - 1]);
+             cnt_h = stdc_leading_zeros (p.tmp[p.tmpsize - 1]);
              incr = (p.tmpsize - p.fracsize) * BITS_PER_MP_LIMB
                     + BITS_PER_MP_LIMB - 1 - cnt_h;
 
@@ -584,7 +584,7 @@ __printf_fp_buffer_1 (struct __printf_buffer *buf, locale_t loc,
                    }
                  else
                    {
-                     count_trailing_zeros (cnt_l, p.tmp[i]);
+                     cnt_l = stdc_trailing_zeros (p.tmp[i]);
 
                      /* Now shift the numbers to their optimal position.  */
                      if (i == 0 && BITS_PER_MP_LIMB - 1 - cnt_h > cnt_l)
@@ -630,7 +630,7 @@ __printf_fp_buffer_1 (struct __printf_buffer *buf, locale_t loc,
          p.tmpsize = p.fracsize;
          assert (cy == 0 || p.tmp[p.tmpsize - 1] < 20);
 
-         count_trailing_zeros (cnt_l, p.tmp[0]);
+         cnt_l = stdc_trailing_zeros (p.tmp[0]);
          if (cnt_l < MIN (4, p.exponent))
            {
              cy = __mpn_lshift (p.frac, p.tmp, p.tmpsize,