From dba703e50368a3cb6de26b42dc2b7682978dfdd5 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Fri, 4 Jun 2021 23:20:50 +0100
Subject: [PATCH] better logging and error reporting

---
 Makefile          |  7 +++++++
 include/cow.hpp   |  2 +-
 src/cow.c         | 29 ++++++++++++++++++++++++-----
 src/test/main.cpp |  4 ++--
 4 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/Makefile b/Makefile
index 17bbfb6..ecd33e2 100644
--- a/Makefile
+++ b/Makefile
@@ -52,6 +52,13 @@ debug: | dirs $(PROJECT)-debug.a
 	-$(MAKE) dirs
 	$(MAKE) $(PROJECT)-debug.so
 
+# Rebuild both release and debug targets from scratch
+.PHONY: all
+all: | clean
+	-$(MAKE) release
+	-$(MAKE) clean-rebuild
+	-$(MAKE) debug
+
 # Targets
 
 dirs:
diff --git a/include/cow.hpp b/include/cow.hpp
index 467fbf4..39588f2 100644
--- a/include/cow.hpp
+++ b/include/cow.hpp
@@ -39,6 +39,7 @@ struct Cow {
 
 struct Cow::Fake : Cow {
 	Fake() = delete;
+	Fake(const Cow& real);
 	Fake(const Fake& copy);
 	Fake(Fake&& move);
 	~Fake();
@@ -50,7 +51,6 @@ struct Cow::Fake : Cow {
 	protected:
 	cow_t* get_raw() const override;
 	private:
-	Fake(const Cow& real);
 
 	cow_t* const fake;
 };
diff --git a/src/cow.c b/src/cow.c
index 1127bcb..de79f11 100644
--- a/src/cow.c
+++ b/src/cow.c
@@ -2,23 +2,35 @@
 
 #include <stdlib.h>
 #include <stdio.h>
-#include <assert.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/mman.h>
 #include <limits.h>
 #include <stddef.h>
+#include <errno.h>
 
 #include <cow.h>
 
+#define LIKELY(ex) __builtin_expect(!!(ex), 1)
+#define UNLIKELY(ex) __builtin_expect(!!(ex), 0)
+
 #define box(t) aligned_alloc(_Alignof(t), sizeof(t))
 
 #if defined(DEBUG) || defined(COW_TRACE)
-#define TRACE(msg, ...) (fprintf(stderr, "[TRACE] %s->%s %d: " msg "\n", __FILE__, __func__, __LINE__, __VA_ARGS__), (void)0)
+#define TRACE(msg, ...) (fprintf(stderr, "<libcow> [TRACE] %s->%s():%d: " msg "\n", __FILE__, __func__, __LINE__, __VA_ARGS__), (void)0)
 #else
 #define TRACE(msg, ...) ((void)0)
 #endif
 
+#if !defined(COW_NO_ASSERT)
+#define ASSERT(expr, msg) do { if(!(expr)) die("assertion failed: `" #expr  "`: " msg);  } while(0)
+#else
+#define ASSERT(op, msg) ((void)0)
+#endif
+
+#define LASSERT(expr, msg) ASSERT(LIKELY(expr), "(unexpected) " msg)
+#define UASSERT(expr, msg) ASSERT(UNLIKELY(expr), "(expected) " msg)
+
 struct cow {
 	void* origin; // ptr to mapped memory. This *MUST* be the first field and have an offset of 0.
 
@@ -30,8 +42,13 @@ _Static_assert(offsetof(cow_t, origin) == 0, "`cow_t.origin` must have an offset
 
 static __attribute__((noreturn)) __attribute__((noinline)) __attribute__((cold)) void die(const char* error)
 {
-	perror(error);
-	exit(1);
+	fprintf(stderr, "<libcow> [FATAL]: ");
+	if(!errno)
+		fprintf(stderr, "%s\n (no matching errno, try compiling with `-DCOW_TRACE` and/or `-DDEBUG`)\n", error);
+	else
+		perror(error);
+
+	abort();
 }
 
 static inline cow_t* box_value(cow_t v)
@@ -39,6 +56,8 @@ static inline cow_t* box_value(cow_t v)
 	cow_t* boxed = box(cow_t);
 	TRACE("boxing cow_t { origin = %p, fd = 0x%x, size = %lu } -> %p (%lu bytes)", v.origin, v.fd, v.size, (const void*)boxed, sizeof(cow_t));
 	*boxed = v;
+
+	LASSERT(cow_ptr(boxed) == boxed->origin, "ptr extraction mismatch. this should never happen (check origin field offset)");
 	return boxed;
 }
 
@@ -81,7 +100,7 @@ cow_t* cow_create(size_t size)
 	ret.origin = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, ret.fd, 0);
 	if(ret.origin == MAP_FAILED) die("cow_create:mmap");
 
-	TRACE("mapped new cow page of %lu size at %p (memfd %d)", size, ret.origin, ret.fd);
+	TRACE("mapped new origin cow page of %lu size at %p (memfd %d)", size, ret.origin, ret.fd);
 	return box_value(ret);
 }
 
diff --git a/src/test/main.cpp b/src/test/main.cpp
index 3e18238..cb2a7a2 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -4,9 +4,9 @@ int main()
 {
 	Cow real(4096);
 
-	Cow::Fake clone = real.clone();
+	Cow::Fake clone = real;
 	{
-		Cow::Fake clone2 = clone.clone();
+		Cow::Fake clone2 = clone;
 	}
 	return 0;
 }