Wrap inflate and other zlib routines for better error reporting

R. Tyler Ballance reported a mysterious transient repository corruption;
after much digging, it turns out that we were not catching and reporting
memory allocation errors from some calls we make to zlib.

This one _just_ wraps things; it doesn't do the "retry on low memory
error" part, at least not yet. It is an independent issue from the
reporting.  Some of the errors are expected and passed back to the caller,
but we die when zlib reports it failed to allocate memory for now.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/wrapper.c b/wrapper.c
index 93562f03ee..c85ca52ec6 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -196,3 +196,63 @@ int xmkstemp(char *template)
 		die("Unable to create temporary file: %s", strerror(errno));
 	return fd;
 }
+
+/*
+ * zlib wrappers to make sure we don't silently miss errors
+ * at init time.
+ */
+void git_inflate_init(z_streamp strm)
+{
+	const char *err;
+
+	switch (inflateInit(strm)) {
+	case Z_OK:
+		return;
+
+	case Z_MEM_ERROR:
+		err = "out of memory";
+		break;
+	case Z_VERSION_ERROR:
+		err = "wrong version";
+		break;
+	default:
+		err = "error";
+	}
+	die("inflateInit: %s (%s)", err, strm->msg ? strm->msg : "no message");
+}
+
+void git_inflate_end(z_streamp strm)
+{
+	if (inflateEnd(strm) != Z_OK)
+		error("inflateEnd: %s", strm->msg ? strm->msg : "failed");
+}
+
+int git_inflate(z_streamp strm, int flush)
+{
+	int ret = inflate(strm, flush);
+	const char *err;
+
+	switch (ret) {
+	/* Out of memory is fatal. */
+	case Z_MEM_ERROR:
+		die("inflate: out of memory");
+
+	/* Data corruption errors: we may want to recover from them (fsck) */
+	case Z_NEED_DICT:
+		err = "needs dictionary"; break;
+	case Z_DATA_ERROR:
+		err = "data stream error"; break;
+	case Z_STREAM_ERROR:
+		err = "stream consistency error"; break;
+	default:
+		err = "unknown error"; break;
+
+	/* Z_BUF_ERROR: normal, needs more space in the output buffer */
+	case Z_BUF_ERROR:
+	case Z_OK:
+	case Z_STREAM_END:
+		return ret;
+	}
+	error("inflate: %s (%s)", err, strm->msg ? strm->msg : "no message");
+	return ret;
+}