[PATCH] Use arc4random instead of rand where available

[Jeremy Huddleston]

Mainly to shut up clang.  These are not security-sensitive uses of rand()

Signed-off-by: Jeremy Huddleston <jeremyhu at apple.com>
---
 configure.ac            |    2 +-
 dix/window.c            |   18 ++++++++++++++++++
 exa/exa_glyphs.c        |    8 ++++++++
 include/dix-config.h.in |    3 +++
 4 files changed, 30 insertions(+), 1 deletions(-)

diff --git a/configure.ac b/configure.ac
index d379b3a..361f380 100644
--- a/configure.ac
+++ b/configure.ac
@@ -206,7 +206,7 @@ dnl Checks for library functions.
 AC_FUNC_VPRINTF
 AC_CHECK_FUNCS([geteuid getuid link memmove memset mkstemp strchr strrchr \
 		strtol getopt getopt_long vsnprintf walkcontext backtrace \
-		getisax getzoneid shmctl64 strcasestr ffs])
+		getisax getzoneid shmctl64 strcasestr ffs arc4random])
 AC_FUNC_ALLOCA
 dnl Old HAS_* names used in os/*.c.
 AC_CHECK_FUNC([getdtablesize],
diff --git a/dix/window.c b/dix/window.c
index c7201df..303cf4d 100644
--- a/dix/window.c
+++ b/dix/window.c
@@ -3189,10 +3189,17 @@ dixSaveScreens(ClientPtr client, int on, int mode)
 		if (logoScreenSaver)
 		    (*pWin->drawable.pScreen->ClearToBackground)(pWin, 0, 0, 0, 0, FALSE);
 #endif
+#ifdef HAVE_ARC4RANDOM
+		(*pWin->drawable.pScreen->MoveWindow)(pWin,
+			   (short)(-(arc4random() % RANDOM_WIDTH)),
+			   (short)(-(arc4random() % RANDOM_WIDTH)),
+			   pWin->nextSib, VTMove);
+#else
 		(*pWin->drawable.pScreen->MoveWindow)(pWin,
 			   (short)(-(rand() % RANDOM_WIDTH)),
 			   (short)(-(rand() % RANDOM_WIDTH)),
 			   pWin->nextSib, VTMove);
+#endif
 #ifndef NOLOGOHACK
 		if (logoScreenSaver)
 		    DrawLogo(pWin);
@@ -3732,7 +3739,11 @@ DrawLogo(WindowPtr pWin)
     if (!pGC)
 	return;
 
+#ifdef HAVE_ARC4RANDOM 
+    if ((arc4random() % 100) <= 17) /* make the probability for white fairly low */
+#else
     if ((rand() % 100) <= 17) /* make the probability for white fairly low */
+#endif
 	fore[0].val = pScreen->whitePixel;
     else
 	fore[0].val = pScreen->blackPixel;
@@ -3776,10 +3787,17 @@ DrawLogo(WindowPtr pWin)
     size = width;
     if (height < width)
 	 size = height;
+#ifdef HAVE_ARC4RANDOM
+    size = RANDOM_WIDTH + arc4random() % (size - RANDOM_WIDTH);
+    size &= ~1;
+    x += arc4random() % (width - size);
+    y += arc4random() % (height - size);
+#else
     size = RANDOM_WIDTH + rand() % (size - RANDOM_WIDTH);
     size &= ~1;
     x += rand() % (width - size);
     y += rand() % (height - size);
+#endif
 
 /*
  * Draw what will be the thin strokes.
diff --git a/exa/exa_glyphs.c b/exa/exa_glyphs.c
index fd14e9b..8c9e591 100644
--- a/exa/exa_glyphs.c
+++ b/exa/exa_glyphs.c
@@ -223,7 +223,11 @@ exaRealizeGlyphCaches(ScreenPtr    pScreen,
 	for (j = 0; j < cache->hashSize; j++)
 	    cache->hashEntries[j] = -1;
 	
+#ifdef HAVE_ARC4RANDOM 
+	cache->evictionPosition = arc4random() % cache->size;
+#else
 	cache->evictionPosition = rand() % cache->size;
+#endif
     }
 
     /* Each cache references the picture individually */
@@ -504,7 +508,11 @@ exaGlyphCacheBufferGlyph(ScreenPtr         pScreen,
 	    exaGlyphCacheHashInsert(cache, pGlyph, pos);
 
 	    /* And pick a new eviction position */
+#ifdef HAVE_ARC4RANDOM 
+	    cache->evictionPosition = arc4random() % cache->size;
+#else
 	    cache->evictionPosition = rand() % cache->size;
+#endif
 	}
 
 	exaGlyphCacheUploadGlyph(pScreen, cache, x, y, pGlyph);
diff --git a/include/dix-config.h.in b/include/dix-config.h.in
index 058c8fd..2ded353 100644
--- a/include/dix-config.h.in
+++ b/include/dix-config.h.in
@@ -54,6 +54,9 @@
 /* Support XDM-AUTH*-1 */
 #undef HASXDMAUTH
 
+/* Define to 1 if you have the `arc4random' function. */
+#undef HAVE_ARC4RANDOM
+
 /* Define to 1 if you have the `getdtablesize' function. */
 #undef HAS_GETDTABLESIZE
 
-- 
1.6.2


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