[gcc r16-3221] real: Eliminate access to uninitialized memory.

[Robert Dubner via Gcc-cvs]

https://gcc.gnu.org/g:810340f9fed56dc2a0e7e1db3f19b383f6e4cb95

commit r16-3221-g810340f9fed56dc2a0e7e1db3f19b383f6e4cb95
Author: Robert Dubner <rdub...@symas.com>
Date:   Thu Jul 31 07:45:26 2025 -0400

    real: Eliminate access to uninitialized memory.
    
    When compiling this program with gcobol:
    
            identification division.
            program-id. prog.
            data division.
            working-storage section.
            01 val pic v9(5) value .001.
            procedure division.
                display val
                goback.
    
    the rounding up of .99999...9999 to 1.000...0000 causes a read of the
    first byte of the output buffer.  Although harmless, it generates a
    valgrind warning.  The following change clears that warning.
    
    gcc/ChangeLog:
    
            * real.cc (real_to_decimal_for_mode): Set str[0] to known value.

Diff:
---
 gcc/real.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/real.cc b/gcc/real.cc
index 1f987d48889f..43d25246ed7c 100644
--- a/gcc/real.cc
+++ b/gcc/real.cc
@@ -1629,6 +1629,11 @@ real_to_decimal_for_mode (char *str, const 
REAL_VALUE_TYPE *r_orig,
       strcpy (str, (r.sign ? "-0.0" : "0.0"));
       return;
     case rvc_normal:
+      /*  When r_orig is a positive value that converts to all nines and is
+          rounded up to 1.0, str[0] is harmlessly accessed before being set to
+          '1'.  That read access triggers a valgrind warning.  Setting str[0]
+          to any value quiets the warning. */
+      str[0] = ' ';
       break;
     case rvc_inf:
       strcpy (str, (r.sign ? "-Inf" : "+Inf"));