diff -Naurd mpfr-4.2.0-a/PATCHES mpfr-4.2.0-b/PATCHES
--- mpfr-4.2.0-a/PATCHES	2023-07-17 13:57:28.913739912 +0000
+++ mpfr-4.2.0-b/PATCHES	2023-07-17 13:57:28.961738687 +0000
@@ -0,0 +1 @@
+strtofr-nullchar
diff -Naurd mpfr-4.2.0-a/VERSION mpfr-4.2.0-b/VERSION
--- mpfr-4.2.0-a/VERSION	2023-07-17 13:56:17.415565464 +0000
+++ mpfr-4.2.0-b/VERSION	2023-07-17 13:57:28.961738687 +0000
@@ -1 +1 @@
-4.2.0-p11
+4.2.0-p12
diff -Naurd mpfr-4.2.0-a/src/mpfr.h mpfr-4.2.0-b/src/mpfr.h
--- mpfr-4.2.0-a/src/mpfr.h	2023-07-17 13:56:17.411565566 +0000
+++ mpfr-4.2.0-b/src/mpfr.h	2023-07-17 13:57:28.957738789 +0000
@@ -27,7 +27,7 @@
 #define MPFR_VERSION_MAJOR 4
 #define MPFR_VERSION_MINOR 2
 #define MPFR_VERSION_PATCHLEVEL 0
-#define MPFR_VERSION_STRING "4.2.0-p11"
+#define MPFR_VERSION_STRING "4.2.0-p12"
 
 /* User macros:
    MPFR_USE_FILE:        Define it to make MPFR define functions dealing
diff -Naurd mpfr-4.2.0-a/src/strtofr.c mpfr-4.2.0-b/src/strtofr.c
--- mpfr-4.2.0-a/src/strtofr.c	2023-01-05 17:09:48.000000000 +0000
+++ mpfr-4.2.0-b/src/strtofr.c	2023-07-17 13:57:28.949738993 +0000
@@ -242,7 +242,10 @@
   pstr->mantissa = NULL;
 
   /* Optional leading whitespace */
-  while (isspace((unsigned char) *str)) str++;
+  /* For non-"C" locales, the ISO C standard allows isspace(0) to
+     return true. So we need to stop explicitly on '\0'. */
+  while (*str != '\0' && isspace ((unsigned char) *str))
+    str++;
 
   /* An optional sign `+' or `-' */
   pstr->negative = (*str == '-');
diff -Naurd mpfr-4.2.0-a/src/version.c mpfr-4.2.0-b/src/version.c
--- mpfr-4.2.0-a/src/version.c	2023-07-17 13:56:17.415565464 +0000
+++ mpfr-4.2.0-b/src/version.c	2023-07-17 13:57:28.961738687 +0000
@@ -25,5 +25,5 @@
 const char *
 mpfr_get_version (void)
 {
-  return "4.2.0-p11";
+  return "4.2.0-p12";
 }