Fix pg_strtof() to not crash on NULL endptr.

tglsfdc · tglsfdc · commit d69c781084f5 · 2025-03-01T14:22:56.000-05:00
We had managed not to notice this simple oversight because none of our calls exercised the case --- until commit 8f42718. That led to pg_dump crashing on any platform that uses this code (currently Cygwin and Mingw). Even though there's no immediate bug in the back branches, backpatch, because a non-POSIX-compliant strtof() substitute is trouble waiting to happen for extensions or future back-patches. Diagnosed-by: Alexander Lakhin <exclusion@gmail.com> Author: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/339b3902-4e98-4e31-a744-94e43b7b9292@gmail.com Backpatch-through: 13
diff --git a/src/port/strtof.c b/src/port/strtof.c
@@ -31,15 +31,18 @@ pg_strtof(const char *nptr, char **endptr)
 {
 	int			caller_errno = errno;
 	float		fresult;
+	char	   *myendptr;
 
 	errno = 0;
-	fresult = (strtof) (nptr, endptr);
+	fresult = (strtof) (nptr, &myendptr);
+	if (endptr)
+		*endptr = myendptr;
 	if (errno)
 	{
 		/* On error, just return the error to the caller. */
 		return fresult;
 	}
-	else if ((*endptr == nptr) || isnan(fresult) ||
+	else if ((myendptr == nptr) || isnan(fresult) ||
 			 ((fresult >= FLT_MIN || fresult <= -FLT_MIN) && !isinf(fresult)))
 	{
 		/*
@@ -53,7 +56,8 @@ pg_strtof(const char *nptr, char **endptr)
 	else
 	{
 		/*
-		 * Try again. errno is already 0 here.
+		 * Try again.  errno is already 0 here, and we assume that the endptr
+		 * won't be any different.
 		 */
 		double		dresult = strtod(nptr, NULL);
 

Original file line number	Diff line number	Diff line change
`@@ -31,15 +31,18 @@ pg_strtof(const char nptr, char *endptr)`
`31`	`31`	`{`
`32`	`32`	`int caller_errno = errno;`
`33`	`33`	`float fresult;`
	`34`	`+ char *myendptr;`
`34`	`35`
`35`	`36`	`errno = 0;`
`36`		`- fresult = (strtof) (nptr, endptr);`
	`37`	`+ fresult = (strtof) (nptr, &myendptr);`
	`38`	`+ if (endptr)`
	`39`	`+ *endptr = myendptr;`
`37`	`40`	`if (errno)`
`38`	`41`	`{`
`39`	`42`	`/* On error, just return the error to the caller. */`
`40`	`43`	`return fresult;`
`41`	`44`	`}`
`42`		`- else if ((*endptr == nptr) \|\| isnan(fresult) \|\|`
	`45`	`+ else if ((myendptr == nptr) \|\| isnan(fresult) \|\|`
`43`	`46`	`((fresult >= FLT_MIN \|\| fresult <= -FLT_MIN) && !isinf(fresult)))`
`44`	`47`	`{`
`45`	`48`	`/*`
`@@ -53,7 +56,8 @@ pg_strtof(const char nptr, char *endptr)`
`53`	`56`	`else`
`54`	`57`	`{`
`55`	`58`	`/*`
`56`		`- * Try again. errno is already 0 here.`
	`59`	`+ * Try again. errno is already 0 here, and we assume that the endptr`
	`60`	`+ * won't be any different.`
`57`	`61`	`*/`
`58`	`62`	`double dresult = strtod(nptr, NULL);`
`59`	`63`