(nuttx) branch master updated: libc: Add Kconfig option to disable hex-string to float parsing

[xiaoxiang]

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xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 0fed06190b2 libc: Add Kconfig option to disable hex-string to float 
parsing
0fed06190b2 is described below

commit 0fed06190b2be0837039bc2593ee472766a48565
Author: Peter van der Perk <peter.vanderp...@nxp.com>
AuthorDate: Wed Jan 7 10:50:39 2026 +0100

    libc: Add Kconfig option to disable hex-string to float parsing
    
    Introduce CONFIG_LIBC_DISABLE_HEXSTR_TO_FLOAT to remove support for
    parsing hexadecimal floating-point constants (C99 %a) in strtod(),
    strtof(), strtold(), and sscanf("%a"). This feature is rarely used in
    embedded systems and its removal saves significant flash space. Decimal
    float parsing remains unaffected.
    
    Signed-off-by: Peter van der Perk <peter.vanderp...@nxp.com>
---
 libs/libc/stdlib/Kconfig       | 10 ++++++++++
 libs/libc/stdlib/lib_strtold.c | 10 ++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/libs/libc/stdlib/Kconfig b/libs/libc/stdlib/Kconfig
index f0cf1cd27d7..d594b4cd8e3 100644
--- a/libs/libc/stdlib/Kconfig
+++ b/libs/libc/stdlib/Kconfig
@@ -46,4 +46,14 @@ config LIBC_MAX_EXITFUNS
                Configure the amount of exit functions for atexit/on_exit. The 
ANSI
                default is 32, but most likely we don't need as many.
 
+config LIBC_DISABLE_HEXSTR_TO_FLOAT
+       bool "Disable hex-string to float/double conversions"
+       default DEFAULT_SMALL
+       ---help---
+               Disables parsing of hexadecimal floating-point constants (C99 
%a),
+               e.g., "0x1.fp3", in strtod(), strtof(), strtold(), and 
sscanf("%a").
+               This saves flash space since hex-float parsing adds significant 
code
+               and is rarely needed in embedded systems. Decimal float parsing 
remains
+               available.
+
 endmenu # stdlib Options
diff --git a/libs/libc/stdlib/lib_strtold.c b/libs/libc/stdlib/lib_strtold.c
index 56a20992bdf..c09c5b885fd 100644
--- a/libs/libc/stdlib/lib_strtold.c
+++ b/libs/libc/stdlib/lib_strtold.c
@@ -432,7 +432,7 @@ static long_double decfloat(FAR char *ptr, FAR char 
**endptr)
  *   A long_double number about ptr
  *
  ****************************************************************************/
-
+#ifndef CONFIG_LIBC_DISABLE_HEXSTR_TO_FLOAT
 static long_double hexfloat(FAR char *ptr,
                             FAR char **endptr, int bits, int emin)
 {
@@ -618,6 +618,7 @@ static long_double hexfloat(FAR char *ptr,
 
   return scalbnx(y, 2., e2);
 }
+#endif
 
 /****************************************************************************
  * Name: strtox
@@ -644,6 +645,7 @@ static long_double strtox(FAR const char *str, FAR char 
**endptr, int flag)
   long_double y = 0;
   int i = 0;
 
+#ifndef CONFIG_LIBC_DISABLE_HEXSTR_TO_FLOAT
   int bits;
   int emin;
 
@@ -664,6 +666,7 @@ static long_double strtox(FAR const char *str, FAR char 
**endptr, int flag)
       default:
         return 0;
     }
+#endif
 
   /* Skip leading whitespace */
 
@@ -712,12 +715,15 @@ static long_double strtox(FAR const char *str, FAR char 
**endptr, int flag)
   /* Process optional 0x prefix */
 
   s -= i;
+#ifndef CONFIG_LIBC_DISABLE_HEXSTR_TO_FLOAT
   if (*s == '0' && (*(s + 1) | 32) == 'x')
     {
       s += 2;
       y = hexfloat(s, endptr, bits, emin);
     }
-  else if (isdigit(*s) || (*s == '.' && isdigit(*(s + 1))))
+  else
+#endif
+  if (isdigit(*s) || (*s == '.' && isdigit(*(s + 1))))
     {
       y = decfloat(s, endptr);
     }