profiler: Support external SysprofCaptureWritersgbsneto/external-capture-writer

Using environment variables to control the profiler is limiting,
and when it comes to GNOME Shell, it adds an extra level of
complexity, since it forces us to start GNOME Shell with the
right environment set.

Add support for setting a caller-controlled SysprofCaptureWriter.
The header file treats it as a gpointer to avoid including config.h.
If an external capture writer is set, it takes precedence over the
filename and the file descriptor.

1 files changed, 30 insertions, 1 deletions

diff --git a/gjs/profiler.cpp b/gjs/profiler.cpp
index c5113bec..d7c90ef5 100644
--- a/gjs/profiler.cpp
+++ b/gjs/profiler.cpp
@@ -105,6 +105,8 @@ struct _GjsProfiler {
     /* Buffers and writes our sampled stacks */
     SysprofCaptureWriter* capture;
     GSource* periodic_flush;
+
+    SysprofCaptureWriter* target_capture;
 #endif  /* ENABLE_PROFILER */
 
     /* The filename to write to */
@@ -259,6 +261,7 @@ _gjs_profiler_free(GjsProfiler *self)
 #ifdef ENABLE_PROFILER
     g_clear_pointer(&self->capture, sysprof_capture_writer_unref);
     g_clear_pointer(&self->periodic_flush, g_source_destroy);
+    g_clear_pointer(&self->target_capture, sysprof_capture_writer_unref);
 
     if (self->fd != -1)
         close(self->fd);
@@ -429,7 +432,9 @@ gjs_profiler_start(GjsProfiler *self)
     struct itimerspec its = { 0 };
     struct itimerspec old_its;
 
-    if (self->fd != -1) {
+    if (self->target_capture) {
+        self->capture = sysprof_capture_writer_ref(self->target_capture);
+    } else if (self->fd != -1) {
         self->capture = sysprof_capture_writer_new_from_fd(self->fd, 0);
         self->fd = -1;
     } else {
@@ -673,6 +678,30 @@ gjs_profiler_chain_signal(GjsContext *context,
 }
 
 /**
+ * gjs_profiler_set_capture_writer:
+ * @self: A #GjsProfiler
+ * @capture: (nullable): A #SysprofCaptureWriter
+ *
+ * Set the capture writer to which profiling data is written when the @self
+ * is stopped.
+ */
+void gjs_profiler_set_capture_writer(GjsProfiler* self, gpointer capture) {
+    g_return_if_fail(self);
+    g_return_if_fail(!self->running);
+
+#ifdef ENABLE_PROFILER
+    g_clear_pointer(&self->target_capture, sysprof_capture_writer_unref);
+    self->target_capture =
+        capture ? sysprof_capture_writer_ref(
+                      reinterpret_cast<SysprofCaptureWriter*>(capture))
+                : NULL;
+#else
+    // Unused in the no-profiler case
+    (void)capture;
+#endif
+}
+
+/**
  * gjs_profiler_set_filename:
  * @self: A #GjsProfiler
  * @filename: string containing a filename