Fix pg_strtof() to not crash on NULL endptr.

We had managed not to notice this simple oversight because none
of our calls exercised the case --- until commit 8f427187d.
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
index 7da05be687bb9f52277525a5f5a2a637d194d793..9ede9d297e6977314f063367dbb4cce6fd17699e 100644 (file)
--- 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);