PATCH: Coverity CID 1637382 bsiz can overflow when reading a large heredoc

Use a size_t and explicit size check, although presumably the realloc
will fail long before we get to this point. In theory if we did, though,
the code would loop forever with bsiz==0 which wouldn't be great.
---
 Src/exec.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Src/exec.c b/Src/exec.c
index 7ea669f35b..2c730b9109 100644
--- a/Src/exec.c
+++ b/Src/exec.c
@@ -4574,7 +4574,8 @@ char *
 gethere(char **strp, int typ)
 {
     char *buf;
-    int bsiz, qt = 0, strip = 0;
+    int qt = 0, strip = 0;
+    size_t bsiz;
     char *s, *t, *bptr, c;
     char *str = *strp;
 
@@ -4601,7 +4602,7 @@ gethere(char **strp, int typ)
 	    if (bptr >= buf + bsiz - 2) {
 		ptrdiff_t toff = t - buf;
 		ptrdiff_t bptroff = bptr - buf;
-		char *newbuf = realloc(buf, 2 * bsiz);
+		char *newbuf = (bsiz <= SIZE_MAX / 2 ) ? realloc(buf, 2 * bsiz) : NULL;
 		if (!newbuf) {
 		    /* out of memory */
 		    zfree(buf, bsiz);
-- 
2.38.1