From: Michael Orlitzky <michael@orlitzky.com>
Date: Thu, 24 Oct 2024 12:02:18 +0000 (-0400)
Subject: src/svgtiny.c: add assertions to unlikely error paths
X-Git-Url: https://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=refs%2Fheads%2Flibcss;p=libsvgtiny.git

src/svgtiny.c: add assertions to unlikely error paths

While cleaning up our select_ctx at the end of svgtiny_parse(), we
loop through and get/remove/destroy any sheets it may have. If any of
these operations fails, we catch and propagate the error. However, we
only get/remove/destroy sheets that the libcss API has just told us
are valid. As a result, these error paths should never be taken. To
emphasize that, we add some assertions to the error paths in debug
builds. Production builds will still catch and propagate.
---

diff --git a/src/svgtiny.c b/src/svgtiny.c
index 53ced0a..6938131 100644
--- a/src/svgtiny.c
+++ b/src/svgtiny.c
@@ -808,6 +808,12 @@ cleanup:
 							n_sheets - 1 - i,
 							&sheet);
 		if (css_code != CSS_OK) {
+			/* The API just told us that there were n_sheets
+			 * valid sheets. So while we attempt to handle
+			 * the error gracefully in production builds,
+			 * this should never happen. */
+			assert(0);
+
 			if (code == svgtiny_OK) {
 				code = svgtiny_LIBCSS_ERROR;
 			}
@@ -821,6 +827,11 @@ cleanup:
 		 * will not try to access them. */
 		css_code = css_select_ctx_remove_sheet(state.select_ctx, sheet);
 		if (css_code != CSS_OK) {
+			/* Same as the assert() above. This sheet arose
+			 * from a call to css_select_ctx_get_sheet() a
+			 * moment ago, it should be valid! */
+			assert(0);
+
 			if (code == svgtiny_OK) {
 				code = svgtiny_LIBCSS_ERROR;
 			}
@@ -831,8 +842,14 @@ cleanup:
 			continue;
 		}
 		css_code = css_stylesheet_destroy((css_stylesheet*)sheet);
-		if (css_code != CSS_OK && code == svgtiny_OK) {
-		  code = svgtiny_LIBCSS_ERROR;
+		if (css_code != CSS_OK) {
+			/* Once more, "sheet" should have been valid
+			 * and un-destroyed. */
+			assert(0);
+
+			if (code == svgtiny_OK) {
+				code = svgtiny_LIBCSS_ERROR;
+			}
 		}
 	}
 	css_code = css_select_ctx_destroy(state.select_ctx);