Fix compilation when checkpoints are enabled.

- Include string.h in checkpoint.h
- Check return values of fgets calls in checkpoint.h.
- Replace variable length array in image.c by a dynamically allocated
  array.
- Add -DCHECKPOINTS to CFLAGS in Makefile when CHECKPOINTS is defined.

src/Makefile

@@ -104,6 +104,10 @@ ifndef KVZ_DISABLE_ASM
   endif
 endif
 
+ifdef CHECKPOINTS
+  CFLAGS += -DCHECKPOINTS
+endif
+
 # Compile files in strategy directories with appropriate flags.
 ifeq ($(ARCH), ppc64)
   strategies/altivec/%.o: EXTRA_FLAGS += -maltivec -fno-lto

src/checkpoint.h

@@ -24,6 +24,7 @@
 #ifdef NDEBUG
 #error "CHECKPOINTS require assertions to be enabled!"
 #endif
+#include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -66,7 +67,7 @@ extern int g_ckpt_record; //Do we record?
       g_ckpt_enabled = 0; \
       while (!feof(g_ckpt_file)) { \
         char buffer_file[4096]; \
-        fgets(buffer_file, 4095, g_ckpt_file); \
+        assert(fgets(buffer_file, 4095, g_ckpt_file) != NULL); \
         if (strncmp(buffer_file, buffer_ckpt, 4096)==0) { \
           g_ckpt_enabled = 1; \
           break; \
@@ -82,7 +83,7 @@ extern int g_ckpt_record; //Do we record?
       fprintf(g_ckpt_file, str "\n", __VA_ARGS__); \
     } else if (g_ckpt_enabled) { \
       char buffer_file[4096], buffer_ckpt[4096]; \
-      fgets(buffer_file, 4095, g_ckpt_file); \
+      assert(fgets(buffer_file, 4095, g_ckpt_file) != NULL); \
       snprintf(buffer_ckpt, 4095, str "\n", __VA_ARGS__); \
       if (strncmp(buffer_file, buffer_ckpt, 4096)!=0) { \
         fprintf(stderr, "Checkpoint failed (at %ld):\nFile: %sExec: %s", ftell(g_ckpt_file), buffer_file, buffer_ckpt); \

src/image.c

@@ -477,8 +477,8 @@ void pixels_blit(const kvz_pixel * const orig, kvz_pixel * const dst,
   assert(width <= dst_stride);
 
 #ifdef CHECKPOINTS
+  char *buffer = malloc((3 * width + 1) * sizeof(char));
   for (y = 0; y < height; ++y) {
-    char buffer[3*width];
     int p;
     for (p = 0; p < width; ++p) {
       sprintf((buffer + 3*p), "%02X ", orig[y*orig_stride]);
@@ -486,6 +486,7 @@ void pixels_blit(const kvz_pixel * const orig, kvz_pixel * const dst,
     buffer[3*width] = 0;
     CHECKPOINT("pixels_blit: %04d: %s", y, buffer);
   }
+  FREE_POINTER(buffer);
 #endif //CHECKPOINTS
 
   if (orig == dst) {