Makefile: run fuzzing corpora as normal unit tests in non-fuzzing mode.

diff --git a/Makefile b/Makefile
index f665f8a..3cee618 100644
--- a/Makefile
+++ b/Makefile
@@ -392,10 +392,7 @@ include cln-grpc/Makefile
 endif
 include plugins/Makefile
 include tests/plugins/Makefile
-
-ifneq ($(FUZZING),0)
-	include tests/fuzz/Makefile
-endif
+include tests/fuzz/Makefile
 
 ifneq ($V,1)
 MSGGEN_ARGS := -s
@@ -709,6 +706,7 @@ endif
 # We special case the fuzzing target binaries, as they need to link against libfuzzer,
 # which brings its own main().
 # FUZZER_LIB and LLVM_LDFLAGS are set by configure script on macOS
+ifneq ($(FUZZING),0)
 ifeq ($(OS),Darwin)
 ifneq ($(FUZZER_LIB),)
 FUZZ_LDFLAGS = $(FUZZER_LIB) $(LLVM_LDFLAGS)
@@ -718,9 +716,10 @@ endif
 else
 FUZZ_LDFLAGS = -fsanitize=fuzzer
 endif
+endif
 
 $(ALL_FUZZ_TARGETS):
-	@$(call VERBOSE, "ld $@", $(LINK.o) $(filter-out %.a,$^) $(LOADLIBES) $(EXTERNAL_LDLIBS) $(LDLIBS) libccan.a $(FUZZ_LDFLAGS) -o $@)
+	@$(call VERBOSE, "ld $@", $(LINK.o) $(filter-out %.a,$^) libcommon.a libccan.a $(LOADLIBES) $(EXTERNAL_LDLIBS) $(LDLIBS) $(FUZZ_LDFLAGS) -o $@)
 ifeq ($(OS),Darwin)
 	@$(call VERBOSE, "dsymutil $@", dsymutil $@)
 endif
@@ -841,6 +840,10 @@ update-mocks/%: % $(ALL_GEN_HEADERS) $(ALL_GEN_SOURCES)
 unittest/%: % bolt-precheck
 	BOLTDIR=$(LOCAL_BOLTDIR) $(VG) $(VG_TEST_ARGS) $* > /dev/null
 
+# FIXME: we don't do leak detection on fuzz tests, since they don't have a cleanup function.
+fuzzunittest/%: % bolt-precheck
+	BOLTDIR=$(LOCAL_BOLTDIR) $(VG) $* > /dev/null
+
 # Commands
 MKDIR_P = mkdir -p
 INSTALL = install
diff --git a/common/peer_failed.h b/common/peer_failed.h
index b782e52..5be8ba8 100644
--- a/common/peer_failed.h
+++ b/common/peer_failed.h
@@ -3,6 +3,7 @@
 #include "config.h"
 #include <ccan/compiler/compiler.h>
 #include <ccan/short_types/short_types.h>
+#include <ccan/take/take.h>
 
 struct channel_id;
 struct per_peer_state;
diff --git a/tests/fuzz/Makefile b/tests/fuzz/Makefile
index ce2d397..c2440e9 100644
--- a/tests/fuzz/Makefile
+++ b/tests/fuzz/Makefile
@@ -13,8 +13,13 @@ FUZZ_TARGETS_SRC := $(wildcard tests/fuzz/fuzz-*.c)
 FUZZ_TARGETS_OBJS := $(FUZZ_TARGETS_SRC:.c=.o)
 FUZZ_TARGETS_BIN := $(FUZZ_TARGETS_SRC:.c=)
 
-$(FUZZ_TARGETS_OBJS): $(COMMON_HEADERS) $(WIRE_HEADERS) $(COMMON_SRC)
+$(FUZZ_TARGETS_OBJS): $(COMMON_HEADERS) $(WIRE_HEADERS) $(COMMON_SRC) tests/fuzz/libfuzz.h
 $(FUZZ_TARGETS_BIN): $(LIBFUZZ_OBJS) libcommon.a
 
 ALL_C_SOURCES += $(FUZZ_TARGETS_SRC) $(LIBFUZZ_SRC)
 ALL_FUZZ_TARGETS += $(FUZZ_TARGETS_BIN)
+
+# In non-fuzzing builds, these become normal tests.
+ifneq ($(FUZZING),1)
+check-units: $(FUZZ_TARGETS_BIN:%=fuzzunittest/%)
+endif
diff --git a/tests/fuzz/bolt12.h b/tests/fuzz/bolt12.h
index b5ef5a7..1189248 100644
--- a/tests/fuzz/bolt12.h
+++ b/tests/fuzz/bolt12.h
@@ -144,6 +144,11 @@ size_t LLVMFuzzerCustomCrossOver(const u8 *data1, size_t size1, const u8 *data2,
 	return encoded_size;
 }
 
-void init(int *argc, char ***argv) { common_setup("fuzzer"); }
+void init(int *argc, char ***argv)
+{
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
+}
 
 #endif /* LIGHTNING_TESTS_FUZZ_BOLT12_H */
diff --git a/tests/fuzz/connectd_handshake.h b/tests/fuzz/connectd_handshake.h
index 6412db8..6216e23 100644
--- a/tests/fuzz/connectd_handshake.h
+++ b/tests/fuzz/connectd_handshake.h
@@ -74,7 +74,9 @@ void init(int *argc, char ***argv)
 	assert(devnull >= 0);
 	status_setup_sync(devnull);
 
-	common_setup("fuzzer");
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
 
 	/* These keys are copied from BOLT 8 test vectors, though we use them in
 	 * a different setting.
diff --git a/tests/fuzz/fuzz-addr.c b/tests/fuzz/fuzz-addr.c
index 082c549..a833bc2 100644
--- a/tests/fuzz/fuzz-addr.c
+++ b/tests/fuzz/fuzz-addr.c
@@ -9,7 +9,9 @@
 void init(int *argc, char ***argv)
 {
 	chainparams = chainparams_for_network("bitcoin");
-	common_setup("fuzzer");
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
 }
 
 void run(const uint8_t *data, size_t size)
diff --git a/tests/fuzz/fuzz-bolt11.c b/tests/fuzz/fuzz-bolt11.c
index 5eeeeda..6f706e0 100644
--- a/tests/fuzz/fuzz-bolt11.c
+++ b/tests/fuzz/fuzz-bolt11.c
@@ -18,7 +18,12 @@ size_t LLVMFuzzerCustomCrossOver(const u8 *in1, size_t in1_size, const u8 *in2,
 				 size_t in2_size, u8 *out, size_t max_out_size,
 				 unsigned seed);
 
-void init(int *argc, char ***argv) { common_setup("fuzzer"); }
+void init(int *argc, char ***argv)
+{
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
+}
 
 // Encodes a dummy bolt11 invoice into `fuzz_data` and returns the size of the
 // encoded string.
diff --git a/tests/fuzz/fuzz-bolt12-bech32-decode.c b/tests/fuzz/fuzz-bolt12-bech32-decode.c
index bd3d867..43f5fd2 100644
--- a/tests/fuzz/fuzz-bolt12-bech32-decode.c
+++ b/tests/fuzz/fuzz-bolt12-bech32-decode.c
@@ -8,7 +8,12 @@
 /* Include bolt12.c directly, to gain access to string_to_data(). */
   #include "../../common/bolt12.c"
 
-void init(int *argc, char ***argv) { common_setup("fuzzer"); }
+void init(int *argc, char ***argv)
+{
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
+}
 
 void run(const u8 *data, size_t size)
 {
diff --git a/tests/fuzz/fuzz-channel_id.c b/tests/fuzz/fuzz-channel_id.c
index df3d35e..bf2c2d0 100644
--- a/tests/fuzz/fuzz-channel_id.c
+++ b/tests/fuzz/fuzz-channel_id.c
@@ -10,7 +10,9 @@
 
 void init(int *argc, char ***argv)
 {
-	common_setup("fuzzer");
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
 }
 
 void run(const uint8_t *data, size_t size)
diff --git a/tests/fuzz/fuzz-close_tx.c b/tests/fuzz/fuzz-close_tx.c
index 0fd29e5..d3f3abf 100644
--- a/tests/fuzz/fuzz-close_tx.c
+++ b/tests/fuzz/fuzz-close_tx.c
@@ -12,7 +12,9 @@
 
 void init(int *argc, char ***argv)
 {
-	common_setup("fuzzer");
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
 	chainparams = chainparams_for_network("bitcoin");
 }
 
diff --git a/tests/fuzz/fuzz-codex32.c b/tests/fuzz/fuzz-codex32.c
index 87e2324..eaaccc3 100644
--- a/tests/fuzz/fuzz-codex32.c
+++ b/tests/fuzz/fuzz-codex32.c
@@ -34,7 +34,9 @@ static struct codex32 *codex32_dup(const tal_t *ctx, const struct codex32 *src)
 
 void init(int *argc, char ***argv)
 {
-	common_setup("fuzzer");
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
 }
 
 /* Custom mutator with structure-aware and byte-level mutations */
diff --git a/tests/fuzz/fuzz-cryptomsg.c b/tests/fuzz/fuzz-cryptomsg.c
index c7b7c64..9b3a47f 100644
--- a/tests/fuzz/fuzz-cryptomsg.c
+++ b/tests/fuzz/fuzz-cryptomsg.c
@@ -54,7 +54,9 @@ void init(int *argc, char ***argv)
 	init_cs_in.s_ck = ck;
 	init_cs_in.r_ck = ck;
 
-	common_setup("fuzzer");
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
 }
 
 /* Test that encrypting and decrypting the message does not alter it. */
diff --git a/tests/fuzz/fuzz-initial_channel.c b/tests/fuzz/fuzz-initial_channel.c
index 5549b36..2fa04c2 100644
--- a/tests/fuzz/fuzz-initial_channel.c
+++ b/tests/fuzz/fuzz-initial_channel.c
@@ -23,7 +23,9 @@
 
 void init(int *argc, char ***argv)
 {
-	common_setup("fuzzer");
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
 	int devnull = open("/dev/null", O_WRONLY);
 	status_setup_sync(devnull);
 	chainparams = chainparams_for_network("bitcoin");
diff --git a/tests/fuzz/libfuzz.c b/tests/fuzz/libfuzz.c
index 98c5fd0..78ee006 100644
--- a/tests/fuzz/libfuzz.c
+++ b/tests/fuzz/libfuzz.c
@@ -2,10 +2,18 @@
 
 #include <assert.h>
 #include <ccan/isaac/isaac64.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/grab_file/grab_file.h>
+#include <ccan/tal/path/path.h>
+#include <ccan/tal/tal.h>
 #include <common/pseudorand.h>
+#include <common/setup.h>
+#include <dirent.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/types.h>
 #include <tests/fuzz/libfuzz.h>
+#include <unistd.h>
 
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
 int LLVMFuzzerInitialize(int *argc, char ***argv);
@@ -118,3 +126,38 @@ size_t cross_over(const u8 *in1, size_t in1_size, const u8 *in2,
 				   max_out_size);
 	return overwrite_part(in1, in1_size, in2, in2_size, out, max_out_size);
 }
+
+/* In non-fuzzing builds, these become unit tests which just run the corpora:
+ * this is also good for attaching a debugger to! */
+#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+int main(int argc, char *argv[])
+{
+	DIR *d;
+	struct dirent *di;
+
+	common_setup(argv[0]);
+	assert(chdir("tests/fuzz/corpora") == 0);
+	assert(chdir(path_basename(tmpctx, argv[0])) == 0);
+
+	/* FIXME: Support explicit path args? */
+	init(&argc, &argv);
+	d = opendir(".");
+	while ((di = readdir(d)) != NULL) {
+		u8 *contents;
+		if (streq(di->d_name, ".") || streq(di->d_name, ".."))
+			continue;
+		contents = grab_file(tmpctx, di->d_name);
+		assert(contents);
+		run(contents, tal_bytelen(contents)-1);
+	}
+	closedir(d);
+	common_shutdown();
+}
+
+/* We never call any functions which might call these */
+size_t LLVMFuzzerMutate(uint8_t *data, size_t size, size_t max_size);
+size_t LLVMFuzzerMutate(uint8_t *data, size_t size, size_t max_size)
+{
+	abort();
+}
+#endif /* !FUZZING */
diff --git a/tests/fuzz/wire.h b/tests/fuzz/wire.h
index 23d1ee1..fb2cfc8 100644
--- a/tests/fuzz/wire.h
+++ b/tests/fuzz/wire.h
@@ -21,7 +21,13 @@ static u8 *prefix_arr(const u8 *data, size_t size, u16 prefix)
 }
 
 /* The init function used by all fuzz-wire-* targets. */
-void init(int *argc, char ***argv) { common_setup("fuzzer"); dev_towire_allow_invalid_node_id = true; }
+void init(int *argc, char ***argv)
+{
+	/* Don't call this if we're in unit-test mode, as libfuzz.c does it */
+	if (!tmpctx)
+		common_setup("fuzzer");
+	dev_towire_allow_invalid_node_id = true;
+}
 
 /* Test that decoding arbitrary data does not crash. Then, if the data was
  * successfully decoded, test that encoding and decoding the message does not