Add valgrind memcheck helpers.

Otherwise valgrind tells you when you test a hash; you want to
know if you hash uninitialized memory long before that.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Makefile

@@ -14,7 +14,7 @@ CCAN_OBJS := ccan-crypto-sha256.o ccan-crypto-shachain.o ccan-err.o ccan-tal.o c
 HEADERS := $(wildcard *.h)
 
 CCANDIR := ccan/
-CFLAGS := -g -Wall -I $(CCANDIR)
+CFLAGS := -g -Wall -I $(CCANDIR) -DVALGRIND_HEADERS=1
 LDLIBS := -lcrypto -lprotobuf-c
 $(PROGRAMS): CFLAGS+=-I.
 

bitcoin/shadouble.c

@@ -1,8 +1,9 @@
 #include "shadouble.h"
+#include "valgrind.h"
 
 void sha256_double(struct sha256_double *shadouble, const void *p, size_t len)
 {
-	sha256(&shadouble->sha, p, len);
+	sha256(&shadouble->sha, check_mem(p, len), len);
 	sha256(&shadouble->sha, &shadouble->sha, sizeof(shadouble->sha));
 }
 

bitcoin/tx.c

@@ -5,6 +5,7 @@
 #include <ccan/tal/grab_file/grab_file.h>
 #include <assert.h>
 #include "tx.h"
+#include "valgrind.h"
 
 static void add_varint(varint_t v,
 		       void (*add)(const void *, size_t, void *), void *addp)
@@ -87,7 +88,7 @@ static void add_tx(const struct bitcoin_tx *tx,
 static void add_sha(const void *data, size_t len, void *shactx_)
 {
 	struct sha256_ctx *ctx = shactx_;
-	sha256_update(ctx, data, len);
+	sha256_update(ctx, check_mem(data, len), len);
 }
 
 void sha256_tx(struct sha256_ctx *ctx, const struct bitcoin_tx *tx)
@@ -101,7 +102,7 @@ static void add_linearize(const void *data, size_t len, void *pptr_)
 	size_t oldsize = tal_count(*pptr);
 
 	tal_resize(pptr, oldsize + len);
-	memcpy(*pptr + oldsize, data, len);
+	memcpy(*pptr + oldsize, check_mem(data, len), len);
 }
 
 u8 *linearize_tx(const tal_t *ctx, const struct bitcoin_tx *tx)
@@ -157,7 +158,7 @@ static const u8 *pull(const u8 **cursor, size_t *max, void *copy, size_t n)
 	*max -= n;
 	if (copy)
 		memcpy(copy, p, n);
-	return p;
+	return check_mem(p, n);
 }
 
 static u64 pull_varint(const u8 **cursor, size_t *max)

bitcoin/valgrind.h

@@ -0,0 +1,18 @@
+#ifndef LIGHTNING_VALGRIND_H
+#define LIGHTNING_VALGRIND_H
+
+#ifdef VALGRIND_HEADERS
+#include <valgrind/memcheck.h>
+#elif !defined(VALGRIND_CHECK_MEM_IS_DEFINED)
+#define VALGRIND_CHECK_MEM_IS_DEFINED(p, len)
+#define RUNNING_ON_VALGRIND 0
+#endif
+
+/* Useful for hashing: makes sure we're not hashing crap *before* we use
+ * the hash value for something. */
+static inline void *check_mem(const void *data, size_t len)
+{
+	VALGRIND_CHECK_MEM_IS_DEFINED(data, len);
+	return (void *)data;
+}
+#endif /* LIGHTNING_VALGRIND_H */