[coreboot-gerrit] Change in ...coreboot[master]: util/romcc: Fix parsing of empty string literal

[Jacob Garber (Code Review)]

Jacob Garber has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/32852

Change subject: util/romcc: Fix parsing of empty string literal
......................................................................

util/romcc: Fix parsing of empty string literal

The corner case of an empty string literal was causing romcc to
segfault. This checks if the literal is empty, and if so allocates a
size one buffer for the terminating null character. A test case for
this is added to ensure it doesn't happen again.

Found-by: Coverity CID 1129099
Signed-off-by: Jacob Garber 
Change-Id: I067160a3b9998184f44e4878ef6269f372fe68bb
---
M util/romcc/romcc.c
A util/romcc/tests/simple_test87.c
2 files changed, 13 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/52/32852/1

diff --git a/util/romcc/romcc.c b/util/romcc/romcc.c
index 43be171..4b84d63 100644
--- a/util/romcc/romcc.c
+++ b/util/romcc/romcc.c
@@ -10782,6 +10782,15 @@
    	} while(str < end);
    	type->elements = ptr - buf;
    } while(peek(state) == TOK_LIT_STRING);
+
+	/* buf contains the allocated buffer for the string constant. However,
+	   if buf is NULL, then the string constant is empty, but we still
+	   need to allocate one byte for the null character. */
+	if (buf == NULL) {
+		buf = xmalloc(1, "string_constant");
+		ptr = buf;
+	}
+
    *ptr = '\0';
    type->elements += 1;
    def = triple(state, OP_BLOBCONST, type, 0, 0);
diff --git a/util/romcc/tests/simple_test87.c b/util/romcc/tests/simple_test87.c
new file mode 100644
index 0000000..6a1148c
--- /dev/null
+++ b/util/romcc/tests/simple_test87.c
@@ -0,0 +1,4 @@
+static void main(void)
+{
+	char *x = "";
+}