Bug fix: Fix X pixmap leakage in shadow_paint

- Fix X pixmap leakage in shadow_paint.

- Add the skeleton of a X resource leakage checker.

Makefile

@@ -84,6 +84,12 @@ ifeq "$(NO_C2)" ""
   OBJS += c2.o
 endif
 
+# ==== X resource checker ====
+ifneq "$(ENABLE_XRESCHECK)" ""
+  CFG += -DDEBUG_XRC
+  OBJS += xrescheck.o
+endif
+
 # === Version string ===
 COMPTON_VERSION ?= git-$(shell git describe --always --dirty)-$(shell git log -1 --date=short --pretty=format:%cd)
 CFG += -DCOMPTON_VERSION="\"$(COMPTON_VERSION)\""

src/common.h

@@ -145,8 +145,6 @@
 #define GLX_BACK_BUFFER_AGE_EXT 0x20F4
 #endif
 
-#endif
-
 // === Macros ===
 
 #define MSTR_(s)        #s
@@ -186,6 +184,11 @@
 /// Macro used for shortening some debugging code.
 #define CASESTRRET(s)   case s: return #s
 
+// X resource checker
+#ifdef DEBUG_XRC
+#include "xrescheck.h"
+#endif
+
 // === Constants ===
 #if !(COMPOSITE_MAJOR > 0 || COMPOSITE_MINOR >= 2)
 #error libXcomposite version unsupported
@@ -2514,3 +2517,4 @@ hexdump(const char *data, int len) {
   fflush(stdout);
 }
 
+#endif

src/compton.c

@@ -486,7 +486,9 @@ win_build_shadow(session_t *ps, win *w, double opacity) {
       shadow_picture_argb, 0, 0, 0, 0, 0, 0,
       shadow_image->width, shadow_image->height);
 
+  assert(!w->shadow_paint.pixmap);
   w->shadow_paint.pixmap = shadow_pixmap_argb;
+  assert(!w->shadow_paint.pict);
   w->shadow_paint.pict = shadow_picture_argb;
 
   // Sync it once and only once
@@ -1826,7 +1828,7 @@ paint_all(session_t *ps, XserverRegion region, XserverRegion region_real, win *t
     // Painting shadow
     if (w->shadow) {
       // Lazy shadow building
-      if (!paint_isvalid(ps, &w->shadow_paint))
+      if (!w->shadow_paint.pixmap)
         win_build_shadow(ps, w, 1);
 
       // Shadow is to be painted based on the ignore region of current
@@ -7510,6 +7512,11 @@ session_destroy(session_t *ps) {
   // Flush all events
   XSync(ps->dpy, True);
 
+#ifdef DEBUG_XRC
+  // Report about resource leakage
+  xrc_report_xid();
+#endif
+
   // Free timeouts
   ps->tmout_unredir = NULL;
   timeout_clear(ps);

src/xrescheck.c

@@ -0,0 +1,65 @@
+#include "xrescheck.h"
+
+static xrc_xid_record_t *gs_xid_records = NULL;
+
+#define HASH_ADD_XID(head, xidfield, add) \
+  HASH_ADD(hh, head, xidfield, sizeof(xid), add)
+
+#define HASH_FIND_XID(head, findxid, out) \
+  HASH_FIND(hh, head, findxid, sizeof(xid), out)
+
+#define M_CPY_POS_DATA(prec) \
+  prec->file = file; \
+  prec->func = func; \
+  prec->line = line; \
+
+/**
+ * @brief Add a record of given XID to the allocation table.
+ */
+void
+xrc_add_xid_(XID xid, const char *type, M_POS_DATA_PARAMS) {
+  xrc_xid_record_t *prec = cmalloc(1, xrc_xid_record_t);
+  prec->xid = xid;
+  prec->type = type;
+  M_CPY_POS_DATA(prec);
+
+  HASH_ADD_XID(gs_xid_records, xid, prec);
+}
+
+/**
+ * @brief Delete a record of given XID in the allocation table.
+ */
+void
+xrc_delete_xid_(XID xid, M_POS_DATA_PARAMS) {
+  xrc_xid_record_t *prec = NULL;
+  HASH_FIND_XID(gs_xid_records, &xid, prec);
+  if (!prec) {
+    printf_err("XRC: %s:%d %s(): Can't find XID %#010lx we want to delete.",
+        file, line, func, xid);
+    return;
+  }
+  HASH_DEL(gs_xid_records, prec);
+  free(prec);
+}
+
+/**
+ * @brief Report about issues found in the XID allocation table.
+ */
+void
+xrc_report_xid(void) {
+  for (xrc_xid_record_t *prec = gs_xid_records; prec; prec = prec->hh.next)
+    printf_dbg("XRC: %s:%d %s(): %#010lx (%s) not freed.\n",
+        prec->file, prec->line, prec->func, prec->xid, prec->type);
+}
+
+/**
+ * @brief Clear the XID allocation table.
+ */
+void
+xrc_clear_xid(void) {
+  xrc_xid_record_t *prec = NULL, *ptmp = NULL;
+  HASH_ITER(hh, gs_xid_records, prec, ptmp) {
+    HASH_DEL(gs_xid_records, prec);
+    free(prec);
+  }
+}

src/xrescheck.h

@@ -0,0 +1,70 @@
+#ifndef COMPTON_XRESCHECK_H
+#define COMPTON_XRESCHECK_H
+
+#include "common.h"
+#include <uthash.h>
+
+typedef struct {
+  XID xid;
+  const char *type;
+  const char *file;
+  const char *func;
+  int line;
+  UT_hash_handle hh;
+} xrc_xid_record_t;
+
+#define M_POS_DATA_PARAMS const char *file, int line, const char *func
+#define M_POS_DATA_PASSTHROUGH file, line, func
+#define M_POS_DATA __FILE__, __LINE__, __func__
+
+void
+xrc_add_xid_(XID xid, const char *type, M_POS_DATA_PARAMS);
+
+#define xrc_add_xid(xid, type) xrc_add_xid_(xid, type, M_POS_DATA)
+
+void
+xrc_delete_xid_(XID xid, M_POS_DATA_PARAMS);
+
+#define xrc_delete_xid(xid) xrc_delete_xid_(xid, M_POS_DATA)
+
+void
+xrc_report_xid(void);
+
+void
+xrc_clear_xid(void);
+
+// Pixmap
+
+static inline Pixmap
+XCreatePixmap_(Display *dpy, Drawable drawable,
+    unsigned int width, unsigned int height, unsigned int depth,
+    M_POS_DATA_PARAMS) {
+  Pixmap ret = XCreatePixmap(dpy, drawable, width, height, depth);
+  if (ret)
+    xrc_add_xid_(ret, "Pixmap", M_POS_DATA_PASSTHROUGH);
+  return ret;
+}
+
+#define XCreatePixmap(dpy, drawable, width, height, depth) \
+  XCreatePixmap_(dpy, drawable, width, height, depth, M_POS_DATA)
+
+static inline Pixmap
+XCompositeNameWindowPixmap_(Display *dpy, Window window, M_POS_DATA_PARAMS) {
+  Pixmap ret = XCompositeNameWindowPixmap(dpy, window);
+  if (ret)
+    xrc_add_xid_(ret, "PixmapC", M_POS_DATA_PASSTHROUGH);
+  return ret;
+}
+
+#define XCompositeNameWindowPixmap(dpy, window) \
+  XCompositeNameWindowPixmap_(dpy, window, M_POS_DATA)
+
+static inline void
+XFreePixmap_(Display *dpy, Pixmap pixmap, M_POS_DATA_PARAMS) {
+  XFreePixmap(dpy, pixmap);
+  xrc_delete_xid_(pixmap, M_POS_DATA_PASSTHROUGH);
+}
+
+#define XFreePixmap(dpy, pixmap) XFreePixmap_(dpy, pixmap, M_POS_DATA);
+
+#endif