Avoid accessing pfile[] out of bounds on syntax error at EOF. (#90)

When awk reaches EOF parsing the program file, curpfile is incremented.
However, cursource() uses curpfile without checking it against npfile
which can cause an out of bounds access of pfile[] if there is a syntax
error at the end of the program file.

1 files changed, 1 insertions, 1 deletions

diff --git a/main.c b/main.c
index 535f1aa..a3e0022 100644
--- a/main.c
+++ b/main.c
@@ -256,7 +256,7 @@ int pgetc(void)		/* get 1 character from awk program */
 char *cursource(void)	/* current source file name */
 {
 	if (npfile > 0)
-		return pfile[curpfile];
+		return pfile[curpfile < npfile ? curpfile : curpfile - 1];
 	else
 		return NULL;
 }