pdf: Properly pass on stdio write errors

cairo-pdf was silently ignoring write errors in
_cairo_pdf_surface_finish(). Any write errors that happened here ended
up setting a "status" variable, but the value in this variable was then
unused.

This commit fixes this bug by passing this error on to the caller.

Additionally, this also adds a test case for this behaviour based on
writing to /dev/full. This file is non-standard and thus the test first
checks that this file exists and is writable before trying to write to
it.

This bug was found based on a report from Knut Petersen [0].

[0]: https://lists.cairographics.org/archives/cairo/2021-July/029281.html

Signed-off-by: Uli Schlachter <psychon@znc.in>

1 files changed, 20 insertions, 1 deletions

diff --git a/test/create-for-stream.c b/test/create-for-stream.c
index af1632f14..3e7577a6a 100644
--- a/test/create-for-stream.c
+++ b/test/create-for-stream.c
@@ -28,6 +28,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+#include <unistd.h>
 
 #if CAIRO_HAS_PS_SURFACE
 #include <cairo-ps.h>
@@ -165,11 +166,29 @@ test_surface (const cairo_test_context_t *ctx,
 
     if (status != CAIRO_STATUS_WRITE_ERROR) {
 	cairo_test_log (ctx,
-			"%s: Error: expected \"write error\", but received \"%s\".\n",
+			"%s: Error: expected \"write error\" from bad_write(), but received \"%s\".\n",
 			backend, cairo_status_to_string (status));
 	return CAIRO_TEST_FAILURE;
     }
 
+    /* test propagation of file errors - for now this is unix-only */
+    if (access("/dev/full", W_OK) == 0) {
+	surface = file_constructor ("/dev/full", WIDTH_IN_POINTS, HEIGHT_IN_POINTS);
+	cairo_surface_finish (surface);
+	status = cairo_surface_status (surface);
+	cairo_surface_destroy (surface);
+
+	if (status != CAIRO_STATUS_WRITE_ERROR) {
+	    cairo_test_log (ctx,
+			    "%s: Error: expected \"write error\" from /dev/full, but received \"%s\".\n",
+			    backend, cairo_status_to_string (status));
+	    return CAIRO_TEST_FAILURE;
+	}
+    } else {
+	cairo_test_log (ctx,
+			"/dev/full does not exist; skipping write test.\n");
+    }
+
     /* construct the real surface */
     wc.ctx = ctx;
     wc.status = CAIRO_TEST_SUCCESS;