glcpp: Don't look for backslashes before the beginning of the string.

Fixes a valgrind error.

diff --git a/src/glsl/glcpp/pp.c b/src/glsl/glcpp/pp.c
index 1ce829a..7aa1a96 100644 (file)
--- a/src/glsl/glcpp/pp.c
+++ b/src/glsl/glcpp/pp.c
@@ -93,12 +93,16 @@ remove_line_continuations(glcpp_parser_t *ctx, const char *shader)
        const char *newline;
        while ((newline = strchr(search_start, '\n')) != NULL) {
                const char *backslash = NULL;
+
+               /* # of characters preceding the newline. */
+               int n = newline - shader;
+
                /* Find the preceding '\', if it exists */
-               if (newline[-1] == '\\') {
+               if (n >= 1 && newline[-1] == '\\')
                        backslash = newline - 1;
-               } else if (newline[-1] == '\r' && newline[-2] == '\\') {
+               else if (n >= 2 && newline[-1] == '\r' && newline[-2] == '\\')
                        backslash = newline - 2;
-               }
+
                /* Double backslashes don't count (the backslash is escaped) */
                if (backslash != NULL && backslash[-1] == '\\') {
                        backslash = NULL;