Fix pg_strtof() to not crash on NULL endptr.

tglsfdc · tglsfdc · commit ebe919e95336 · 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
@@ -76,15 +76,18 @@ 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)))
 	{
 		/*
@@ -98,7 +101,8 @@ 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
`@@ -76,15 +76,18 @@ pg_strtof(const char nptr, char *endptr)`
`76`	`76`	`{`
`77`	`77`	`int caller_errno = errno;`
`78`	`78`	`float fresult;`
	`79`	`+ char *myendptr;`
`79`	`80`
`80`	`81`	`errno = 0;`
`81`		`- fresult = (strtof) (nptr, endptr);`
	`82`	`+ fresult = (strtof) (nptr, &myendptr);`
	`83`	`+ if (endptr)`
	`84`	`+ *endptr = myendptr;`
`82`	`85`	`if (errno)`
`83`	`86`	`{`
`84`	`87`	`/* On error, just return the error to the caller. */`
`85`	`88`	`return fresult;`
`86`	`89`	`}`
`87`		`- else if ((*endptr == nptr) \|\| isnan(fresult) \|\|`
	`90`	`+ else if ((myendptr == nptr) \|\| isnan(fresult) \|\|`
`88`	`91`	`((fresult >= FLT_MIN \|\| fresult <= -FLT_MIN) && !isinf(fresult)))`
`89`	`92`	`{`
`90`	`93`	`/*`
`@@ -98,7 +101,8 @@ pg_strtof(const char nptr, char *endptr)`
`98`	`101`	`else`
`99`	`102`	`{`
`100`	`103`	`/*`
`101`		`- * Try again. errno is already 0 here.`
	`104`	`+ * Try again. errno is already 0 here, and we assume that the endptr`
	`105`	`+ * won't be any different.`
`102`	`106`	`*/`
`103`	`107`	`double dresult = strtod(nptr, NULL);`
`104`	`108`