Fixed bug #324 - prevent unaligned load access

use memcpy so we can expect the compiler to optimize when possible (cherry picked from commit d2e6ded)
libsdl-org · Jan 10, 2024 · f75fb29 · f75fb29
1 parent 073da22
commit f75fb29
Showing 1 changed file with 13 additions and 4 deletions.
diff --git a/SDL_ttf.c b/SDL_ttf.c
@@ -416,7 +416,9 @@ static SDL_INLINE void BG_Blended_Color(const TTF_Image *image, Uint32 *destinat
         while (height--) {
             /* *INDENT-OFF* */
             DUFFS_LOOP4(
-                    tmp = *src++;
+                    /* prevent misaligned load: tmp = *src++; */
+                    /* eventually, we can expect the compiler to replace the memcpy call with something optimized */
+                    memcpy(&tmp, src++, sizeof(tmp)); /* This should NOT be SDL_memcpy */
                     alpha = tmp >> 24;
                     tmp &= ~0xFF000000;
                     alpha = fg_alpha * alpha;
@@ -451,7 +453,8 @@ static SDL_INLINE void BG_Blended_LCD(const TTF_Image *image, Uint32 *destinatio
     while (height--) {
         /* *INDENT-OFF* */
         DUFFS_LOOP4(
-                tmp = *src++;
+                /* prevent misaligned load: tmp = *src++; */
+                memcpy(&tmp, src++, sizeof(tmp)); /* This should NOT be SDL_memcpy */
 
                 if (tmp) {
                     bg = *dst;
@@ -908,11 +911,14 @@ static SDL_INLINE void BG_64(const TTF_Image *image, Uint8 *destination, Sint32
     Uint64       *dst    = (Uint64 *)destination;
     Uint32        width  = image->width / 8;
     Uint32        height = image->rows;
+    Uint64        tmp;
 
     while (height--) {
         /* *INDENT-OFF* */
         DUFFS_LOOP4(
-            *dst++ |= *src++;
+              /* prevent misaligned load: *dst++ |= *src++; */
+              memcpy(&tmp, src++, sizeof(tmp)); /* This should NOT be SDL_memcpy */
+              *dst++ |= tmp;
         , width);
         /* *INDENT-ON* */
         src = (const Uint64 *)((const Uint8 *)src + srcskip);
@@ -926,11 +932,14 @@ static SDL_INLINE void BG_32(const TTF_Image *image, Uint8 *destination, Sint32
     Uint32       *dst    = (Uint32 *)destination;
     Uint32        width  = image->width / 4;
     Uint32        height = image->rows;
+    Uint32        tmp;
 
     while (height--) {
         /* *INDENT-OFF* */
         DUFFS_LOOP4(
-            *dst++ |= *src++;
+            /* prevent misaligned load: *dst++ |= *src++; */
+            memcpy(&tmp, src++, sizeof(tmp)); /* This should NOT be SDL_memcpy */
+            *dst++ |= tmp;
         , width);
         /* *INDENT-ON* */
         src = (const Uint32 *)((const Uint8 *)src + srcskip);