[test] Preparatory work for running under memfault.

In order to run under memfault, the framework is first extended to handle
running concurrent tests - i.e. multi-threading. (Not that this is a
requirement for memfault, instead it shares a common goal of storing
per-test data).  To that end all the global data is moved into a per-test
context and the targets are adjusted to avoid overlap on shared, global
resources (such as output files and frame buffers). In order to preserve
the simplicity of the standard draw routines, the context is not passed
explicitly as a parameter to the routines, but is instead attached to the
cairo_t via the user_data.

For the masochist, to enable the tests to be run across multiple threads
simply set the environment variable CAIRO_TEST_NUM_THREADS to the desired
number.

In the long run, we can hope the need for memfault (runtime testing of
error paths) will be mitigated by static analysis. A promising candidate
for this task would appear to be http://hal.cs.berkeley.edu/cil/.

1 files changed, 1 insertions, 1 deletions

diff --git a/test/degenerate-arc.c b/test/degenerate-arc.c
index f01b666b..d030598b 100644
--- a/test/degenerate-arc.c
+++ b/test/degenerate-arc.c
@@ -32,7 +32,7 @@
 
 static cairo_test_draw_function_t draw;
 
-cairo_test_t test = {
+static const cairo_test_t test = {
     "degenerate-arc",
     "Tests the behaviour of degenerate arcs",
     40, 40,