libvisual/lv_bmp.c: Address warning -Wunused-result

Symptom was:
> lv_bmp.c: In function 'visual_bitmap_load':
> lv_bmp.c:286:9: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   286 |         fread (magic, 2, 1, fp);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:294:9: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   294 |         fread (&bf_size, 4, 1, fp);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:301:9: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   301 |         fread (&bf_bits, 4, 1, fp);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:305:9: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   305 |         fread (&bi_size, 4, 1, fp);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:310:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   310 |                 fread (&bi_width, 2, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:311:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   311 |                 fread (&bi_height, 2, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:319:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   319 |                 fread (&bi_bitcount, 2, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:324:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   324 |                 fread (&bi_width, 4, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:325:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   325 |                 fread (&bi_height, 4, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:333:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   333 |                 fread (&bi_bitcount, 2, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:337:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   337 |                 fread (&bi_compression, 4, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> lv_bmp.c:344:17: warning: ignoring return value of 'fread' declared with attribute 'warn_unused_result' [-Wunused-result]
>   344 |                 fread (&bi_clrused, 4, 1, fp);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Author: hartwork

libvisual/libvisual/lv_bmp.c

@@ -283,65 +283,89 @@ int visual_bitmap_load (VisVideo *video, const char *filename)
 	}
 
 	/* Read the magic string */
-	fread (magic, 2, 1, fp);
+	if (fread (magic, 2, 1, fp) != 1) {
+		return -VISUAL_ERROR_BMP_NO_BMP;
+	}
 	if (strncmp (magic, "BM", 2) != 0) {
 		visual_log (VISUAL_LOG_WARNING, _("Not a bitmap file")); 
 		fclose (fp);
 		return -VISUAL_ERROR_BMP_NO_BMP;
 	}
 
 	/* Read the file size */
-	fread (&bf_size, 4, 1, fp);
+	if (fread (&bf_size, 4, 1, fp) != 1) {
+		return -VISUAL_ERROR_BMP_CORRUPTED;
+	}
 	bf_size = VISUAL_ENDIAN_LEI32 (bf_size);
 
 	/* Skip past the reserved bits */
 	fseek (fp, 4, SEEK_CUR);
 
 	/* Read the offset bits */
-	fread (&bf_bits, 4, 1, fp);
+	if (fread (&bf_bits, 4, 1, fp) != 1) {
+		return -VISUAL_ERROR_BMP_CORRUPTED;
+	}
 	bf_bits = VISUAL_ENDIAN_LEI32 (bf_bits);
 
 	/* Read the info structure size */
-	fread (&bi_size, 4, 1, fp);
+	if (fread (&bi_size, 4, 1, fp) != 1) {
+		return -VISUAL_ERROR_BMP_CORRUPTED;
+	}
 	bi_size = VISUAL_ENDIAN_LEI32 (bi_size);
 
 	if (bi_size == 12) {
 		/* And read the width, height */
-		fread (&bi_width, 2, 1, fp);
-		fread (&bi_height, 2, 1, fp);
+		if (fread (&bi_width, 2, 1, fp) != 1) {
+			return -VISUAL_ERROR_BMP_CORRUPTED;
+		}
+		if (fread (&bi_height, 2, 1, fp) != 1) {
+	    return -VISUAL_ERROR_BMP_CORRUPTED;
+	}
 		bi_width = VISUAL_ENDIAN_LEI16 (bi_width);
 		bi_height = VISUAL_ENDIAN_LEI16 (bi_height);
 
 		/* Skip over the planet */
 		fseek (fp, 2, SEEK_CUR);
 
 		/* Read the bits per pixel */
-		fread (&bi_bitcount, 2, 1, fp);
+		if (fread (&bi_bitcount, 2, 1, fp) != 1) {
+			return -VISUAL_ERROR_BMP_CORRUPTED;
+		}
 		bi_bitcount = VISUAL_ENDIAN_LEI16 (bi_bitcount);
 		bi_compression = BI_RGB;
 	} else {
 		/* And read the width, height */
-		fread (&bi_width, 4, 1, fp);
-		fread (&bi_height, 4, 1, fp);
+		if (fread (&bi_width, 4, 1, fp) != 1) {
+			return -VISUAL_ERROR_BMP_CORRUPTED;
+		}
+		if (fread (&bi_height, 4, 1, fp) != 1) {
+			return -VISUAL_ERROR_BMP_CORRUPTED;
+		}
 		bi_width = VISUAL_ENDIAN_LEI32 (bi_width);
 		bi_height = VISUAL_ENDIAN_LEI32 (bi_height);
 
 		/* Skip over the planet */
 		fseek (fp, 2, SEEK_CUR);
 
 		/* Read the bits per pixel */
-		fread (&bi_bitcount, 2, 1, fp);
+		if (fread (&bi_bitcount, 2, 1, fp) != 1) {
+			return -VISUAL_ERROR_BMP_CORRUPTED;
+		}
 		bi_bitcount = VISUAL_ENDIAN_LEI16 (bi_bitcount);
 
 		/* Read the compression flag */
-		fread (&bi_compression, 4, 1, fp);
+		if (fread (&bi_compression, 4, 1, fp) != 1) {
+			return -VISUAL_ERROR_BMP_CORRUPTED;
+		}
 		bi_compression = VISUAL_ENDIAN_LEI32 (bi_compression);
 
 		/* Skip over the nonsense we don't want to know */
 		fseek (fp, 12, SEEK_CUR);
 
 		/* Number of colors in palette */
-		fread (&bi_clrused, 4, 1, fp);
+		if (fread (&bi_clrused, 4, 1, fp) != 1) {
+			return -VISUAL_ERROR_BMP_CORRUPTED;
+		}
 		bi_clrused = VISUAL_ENDIAN_LEI32 (bi_clrused);
 
 		/* Skip over the other nonsense */