gcc 13 does not like this loop (on i686):

			while (strlen(mybuf) + strlen(s) > bufsz) {
				bufsz *= 2;
				mybuf = (char *) g_realloc(mybuf, bufsz);
			}

and ends up deciding that bufsz may become -1 leading to this compile error:

In file included from /usr/include/stdio.h:959,
                 from mdb-sql.c:19:
In function 'fgets',
    inlined from 'main' at mdb-sql.c:423:9:
/usr/include/bits/stdio2.h:213:12: error: argument 2 value -1 is negative [-Werror=stringop-overflow=]
  213 |     return __fgets_alias (__s, __n, __stream);
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/features.h:503,
                 from /usr/include/bits/libc-header-start.h:33,
                 from /usr/include/stdio.h:27:
/usr/include/bits/stdio2.h: In function 'main':
/usr/include/bits/stdio2.h:198:14: note: in a call to function '*fgets' declared with attribute 'access (write_only, 1, 2)'
  198 | extern char *__REDIRECT (__fgets_alias,
      |              ^~~~~~~~~~
cc1: all warnings being treated as errors
make[3]: *** [Makefile:709: mdb-sql.o] Error 1

Only the size of the buffer which stores all statements until the "go"
command needs to grow dynamically. Limit reading of input to always read
4096 bytes lines or chunks. Which matches the size which the old code
would always use for the first line read.

This makes mdb-sql.c build again on i686 with gcc 13.

diff -up mdbtools-0.9.3/src/util/mdb-sql.c~ mdbtools-0.9.3/src/util/mdb-sql.c
--- mdbtools-0.9.3/src/util/mdb-sql.c~	2023-03-23 15:05:26.000000000 +0100
+++ mdbtools-0.9.3/src/util/mdb-sql.c	2023-03-23 15:14:09.719333781 +0100
@@ -321,6 +321,7 @@ int
 main(int argc, char **argv)
 {
 	char *s = NULL;
+	const int s_bufsz = 4096;
 	char prompt[20];
 	int line = 0;
 	char *mybuf;
@@ -420,8 +420,8 @@ main(int argc, char **argv)
 		}
 
 		if (in) {
-			s=calloc(bufsz, 1);
-			if (!fgets(s, bufsz, in)) {
+			s=calloc(s_bufsz, 1);
+			if (!fgets(s, s_bufsz, in)) {
 				// Backwards compatibility with older MDBTools
 				// Files read from the command line had an
 				// implicit "go" at the end