trace: handle NULL argument in trace_disable()

All of the trace functions treat a NULL key as a synonym for
the default GIT_TRACE key. Except for trace_disable(), which
will segfault.

Fortunately, this can't cause any bugs, as the function has
no callers. But rather than drop it, let's fix the bug, as I
plan to add a caller.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/trace.c b/trace.c
index 4aeea60973100bfed212842cb46a5a81154b7781..f204a7d88a03261403f2f93b5525ac2cc4646446 100644 (file)
--- a/trace.c
+++ b/trace.c
@@ -25,15 +25,25 @@
 #include "cache.h"
 #include "quote.h"
 
+/*
+ * "Normalize" a key argument by converting NULL to our trace_default,
+ * and otherwise passing through the value. All caller-facing functions
+ * should normalize their inputs in this way, though most get it
+ * for free by calling get_trace_fd() (directly or indirectly).
+ */
+static void normalize_trace_key(struct trace_key **key)
+{
+       static struct trace_key trace_default = { "GIT_TRACE" };
+       if (!*key)
+               *key = &trace_default;
+}
+
 /* Get a trace file descriptor from "key" env variable. */
 static int get_trace_fd(struct trace_key *key)
 {
-       static struct trace_key trace_default = { "GIT_TRACE" };
        const char *trace;
 
-       /* use default "GIT_TRACE" if NULL */
-       if (!key)
-               key = &trace_default;
+       normalize_trace_key(&key);
 
        /* don't open twice */
        if (key->initialized)
@@ -75,6 +85,8 @@ static int get_trace_fd(struct trace_key *key)
 
 void trace_disable(struct trace_key *key)
 {
+       normalize_trace_key(&key);
+
        if (key->need_close)
                close(key->fd);
        key->fd = 0;