[Piglit] [PATCH] texturing/s3tc-errors: double check GL_TEXTURE parameters and alloc

[Daniel Kurtz]

If the GL does not actually support one of the compression
formats in s3tc_formats, it may silently choose a different actual
internalformat.

In such a case, the resulting compressed image size may be larger,
leading to memory corruption when the bigger-than-expected image is read back
with glGetCompressedTexImage() into a buffer that was allocated to the
expected, smaller, size.

Instead, first confirm the texture has really been compressed, that the
format is as expected, and that the size matches our pre-computed expected
size.  If any of these fail, set pass to false and spit an error, but
keep going, using the actual format and size returned by the GL.

Ian Romanick pointed out that "if we're going to all this effort, we should
probably go all the way. A follow-on patch should check that
glGetCompressedTexImage doesn't over-run the buffer.

Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
---
v2:
 * Fixed parameter check block format per Ian Romanick review
 * Updated commit message title per Brian Paul review
 * Function call continuation lines align with open '(' (like in rest of file).

 Note: I am new to piglit, so do not have commit access.

 tests/texturing/s3tc-errors.c | 46 +++++++++++++++++++++++++++++++++++++++----
 1 file changed, 42 insertions(+), 4 deletions(-)

diff --git a/tests/texturing/s3tc-errors.c b/tests/texturing/s3tc-errors.c
index 710625c..19a871b 100644
--- a/tests/texturing/s3tc-errors.c
+++ b/tests/texturing/s3tc-errors.c
@@ -125,14 +125,17 @@ check_gl_error2_(GLenum err1, GLenum err2, int line)
 
 
 static bool
-test_format(int width, int height, GLfloat *image, GLenum format)
+test_format(int width, int height, GLfloat *image, GLenum requested_format)
 {
-	GLubyte *compressed_image =
-		malloc(piglit_compressed_image_size(format, width, height));
+	GLubyte *compressed_image;
 	GLenum format2;
 	int x, y, w, h;
 	GLuint tex;
 	bool pass = true;
+	GLuint expected_size;
+	bool is_compressed;
+	GLuint compressed_size;
+	GLenum format;
 
 	glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
 	glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
@@ -143,12 +146,47 @@ test_format(int width, int height, GLfloat *image, GLenum format)
 	glBindTexture(GL_TEXTURE_2D, tex);
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-	glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0,
+	glTexImage2D(GL_TEXTURE_2D, 0, requested_format, width, height, 0,
 		     GL_RGBA, GL_FLOAT, image);
 
 	pass = piglit_check_gl_error(GL_NO_ERROR) && pass;
 	pass = check_rendering(width, height) && pass;
 
+	glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_COMPRESSED,
+				 &is_compressed);
+	glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_INTERNAL_FORMAT,
+				 &format);
+	glGetTexLevelParameteriv(GL_TEXTURE_2D, 0,
+				 GL_TEXTURE_COMPRESSED_IMAGE_SIZE,
+				 &compressed_size);
+
+	pass = piglit_check_gl_error(GL_NO_ERROR) && pass;
+
+	if (!is_compressed) {
+		printf("Image was not compressed\n");
+		pass = false;
+	}
+
+	if (format != requested_format) {
+		printf("Internal Format mismatch. Found: 0x%04x Expected: 0x%04x\n",
+		       format, requested_format);
+		pass = false;
+	}
+
+	expected_size = piglit_compressed_image_size(requested_format, width,
+			height);
+
+	if (compressed_size != expected_size) {
+		printf("Compressed image size mismatch. Found: %u Expected: %u\n",
+		       compressed_size, expected_size);
+		pass = false;
+	}
+
+	/* Use GL_TEXTURE_COMPRESSED_IMAGE_SIZE even if it wasn't what we
+	 * expected to avoid corruption due to under-allocated buffer.
+	 */
+	compressed_image = malloc(compressed_size);
+
 	/* Read back the compressed image data */
 	glGetCompressedTexImage(GL_TEXTURE_2D, 0, compressed_image);
 
-- 
1.9.0.rc1.175.g0b1dcb5