error-handling: On-disk config file backend

Includes:

	- Proper error reporting when encountering syntax errors in a
	config file (file, line number, column).

	- Rewritten `config_write`, now with 99% less goto-spaghetti

	- Error state in `git_filebuf`: filebuf write functions no longer
	need to be checked for error returns. If any of the writes performed
	on a buffer fail, the last call to `git_filebuf_commit` or
	`git_filebuf_hash` will fail accordingly and set the appropiate error
	message. Baller!

include/git2/errors.h

@@ -127,14 +127,9 @@ typedef enum {
 	GITERR_ZLIB,
 	GITERR_REPOSITORY,
 	GITERR_CONFIG,
+	GITERR_REGEX,
 } git_error_class;
 
-#define GITERR_CHECK_ALLOC(ptr) if (ptr == NULL) { return -1; }
-
-GIT_EXTERN(void) giterr_set_oom(void);
-GIT_EXTERN(void) giterr_set(int error_class, const char *string, ...);
-GIT_EXTERN(void) giterr_clear(void);
-
 /**
  * Return a detailed error string with the latest error
  * that occurred in the library.

src/common.h

@@ -46,6 +46,8 @@
 #include "thread-utils.h"
 #include "bswap.h"
 
+#include <regex.h>
+
 extern void git___throw(const char *, ...) GIT_FORMAT_PRINTF(1, 2);
 #define git__throw(error, ...) \
 	(git___throw(__VA_ARGS__), error)
@@ -54,6 +56,16 @@ extern void git___rethrow(const char *, ...) GIT_FORMAT_PRINTF(1, 2);
 #define git__rethrow(error, ...) \
 	(git___rethrow(__VA_ARGS__), error)
 
+
+#define GITERR_CHECK_ALLOC(ptr) if (ptr == NULL) { return -1; }
+
+void giterr_set_oom(void);
+void giterr_set(int error_class, const char *string, ...);
+void giterr_clear(void);
+void giterr_set_str(int error_class, const char *string);
+void giterr_set_regex(const regex_t *regex, int error_code);
+
+
 #include "util.h"
 
 

src/config.c

@@ -401,13 +401,15 @@ int git_config_get_string(git_config *cfg, const char *name, const char **out)
 		if (ret == 0)
 			return 0;
 
+		/* File backend doesn't set error message on variable
+		 * not found */
 		if (ret == GIT_ENOTFOUND)
 			continue;
 
 		return ret;
 	}
 
-	giterr_set(GITERR_CONFIG, "Config value '%s' not found", name);
+	giterr_set(GITERR_CONFIG, "Config variable '%s' not found", name);
 	return GIT_ENOTFOUND;
 }
 

src/errors.c

@@ -122,25 +122,28 @@ void giterr_set(int error_class, const char *string, ...)
 {
 	char error_str[1024];
 	va_list arglist;
-	git_error *error;
-	const char *oserr =
-		(error_class == GITERR_OS && errno != 0) ? strerror(errno) : NULL;
-
-	error = &GIT_GLOBAL->error_t;
-	free(error->message);
 
 	va_start(arglist, string);
 	p_vsnprintf(error_str, sizeof(error_str), string, arglist);
 	va_end(arglist);
 
 	/* automatically suffix strerror(errno) for GITERR_OS errors */
-	if (oserr != NULL) {
+	if (error_class == GITERR_OS) {
 		strncat(error_str, ": ", sizeof(error_str));
-		strncat(error_str, oserr, sizeof(error_str));
+		strncat(error_str, strerror(errno), sizeof(error_str));
 		errno = 0;
 	}
 
-	error->message = git__strdup(error_str);
+	giterr_set_str(error_class, error_str);
+}
+
+void giterr_set_str(int error_class, const char *string)
+{
+	git_error *error = &GIT_GLOBAL->error_t;
+
+	free(error->message);
+
+	error->message = git__strdup(string);
 	error->klass = error_class;
 
 	if (error->message == NULL) {
@@ -151,6 +154,13 @@ void giterr_set(int error_class, const char *string, ...)
 	GIT_GLOBAL->last_error = error;
 }
 
+void giterr_set_regex(const regex_t *regex, int error_code)
+{
+	char error_buf[1024];
+	regerror(error_code, regex, error_buf, sizeof(error_buf));
+	giterr_set_str(GITERR_REGEX, error_buf);
+}
+
 void giterr_clear(void)
 {
 	GIT_GLOBAL->last_error = NULL;

src/filebuf.c

@@ -14,6 +14,36 @@
 
 static const size_t WRITE_BUFFER_SIZE = (4096 * 2);
 
+enum buferr_t {
+	BUFERR_OK = 0,
+	BUFERR_WRITE,
+	BUFERR_ZLIB,
+	BUFERR_MEM
+};
+
+#define ENSURE_BUF_OK(buf) if ((buf)->last_error != BUFERR_OK) { return -1; }
+
+static int verify_last_error(git_filebuf *file)
+{
+	switch (file->last_error) {
+	case BUFERR_WRITE:
+		giterr_set(GITERR_OS, "Failed to write out file");
+		return -1;
+
+	case BUFERR_MEM:
+		giterr_set_oom();
+		return -1;
+
+	case BUFERR_ZLIB:
+		giterr_set(GITERR_ZLIB,
+			"Buffer error when writing out ZLib data");
+		return -1;
+
+	default:
+		return 0;
+	}
+}
+
 static int lock_file(git_filebuf *file, int flags)
 {
 	if (git_path_exists(file->path_lock) == true) {
@@ -100,20 +130,21 @@ GIT_INLINE(int) flush_buffer(git_filebuf *file)
 
 static int write_normal(git_filebuf *file, void *source, size_t len)
 {
-	int result = 0;
-
 	if (len > 0) {
-		result = p_write(file->fd, (void *)source, len);
+		if (p_write(file->fd, (void *)source, len) < 0) {
+			file->last_error = BUFERR_WRITE;
+			return -1;
+		}
+
 		if (file->digest)
 			git_hash_update(file->digest, source, len);
 	}
 
-	return result;
+	return 0;
 }
 
 static int write_deflate(git_filebuf *file, void *source, size_t len)
 {
-	int result = Z_OK;
 	z_stream *zs = &file->zs;
 
 	if (len > 0 || file->flush_mode == Z_FINISH) {
@@ -126,14 +157,17 @@ static int write_deflate(git_filebuf *file, void *source, size_t len)
 			zs->next_out = file->z_buf;
 			zs->avail_out = (uInt)file->buf_size;
 
-			result = deflate(zs, file->flush_mode);
-			if (result == Z_STREAM_ERROR)
-				return git__throw(GIT_ERROR, "Failed to deflate input");
+			if (deflate(zs, file->flush_mode) == Z_STREAM_ERROR) {
+				file->last_error = BUFERR_ZLIB;
+				return -1;
+			}
 
 			have = file->buf_size - (size_t)zs->avail_out;
 
-			if (p_write(file->fd, file->z_buf, have) < GIT_SUCCESS)
-				return git__throw(GIT_EOSERR, "Failed to write to file");
+			if (p_write(file->fd, file->z_buf, have) < 0) {
+				file->last_error = BUFERR_WRITE;
+				return -1;
+			}
 
 		} while (zs->avail_out == 0);
 
@@ -143,7 +177,7 @@ static int write_deflate(git_filebuf *file, void *source, size_t len)
 			git_hash_update(file->digest, source, len);
 	}
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_filebuf_open(git_filebuf *file, const char *path, int flags)
@@ -161,6 +195,7 @@ int git_filebuf_open(git_filebuf *file, const char *path, int flags)
 	file->buf_size = WRITE_BUFFER_SIZE;
 	file->buf_pos = 0;
 	file->fd = -1;
+	file->last_error = BUFERR_OK;
 
 	/* Allocate the main cache buffer */
 	file->buffer = git__malloc(file->buf_size);
@@ -237,58 +272,61 @@ cleanup:
 
 int git_filebuf_hash(git_oid *oid, git_filebuf *file)
 {
-	int error;
-
 	assert(oid && file && file->digest);
 
-	if ((error = flush_buffer(file)) < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to get hash for file");
+	flush_buffer(file);
+
+	if (verify_last_error(file) < 0)
+		return -1;
 
 	git_hash_final(oid, file->digest);
 	git_hash_free_ctx(file->digest);
 	file->digest = NULL;
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_filebuf_commit_at(git_filebuf *file, const char *path, mode_t mode)
 {
 	git__free(file->path_original);
 	file->path_original = git__strdup(path);
-	if (file->path_original == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(file->path_original);
 
 	return git_filebuf_commit(file, mode);
 }
 
 int git_filebuf_commit(git_filebuf *file, mode_t mode)
 {
-	int error;
-
 	/* temporary files cannot be committed */
 	assert(file && file->path_original);
 
 	file->flush_mode = Z_FINISH;
-	if ((error = flush_buffer(file)) < GIT_SUCCESS)
-		goto cleanup;
+	flush_buffer(file);
+
+	if (verify_last_error(file) < 0)
+		goto on_error;
 
 	p_close(file->fd);
 	file->fd = -1;
 
 	if (p_chmod(file->path_lock, mode)) {
-		error = git__throw(GIT_EOSERR, "Failed to chmod locked file before committing");
-		goto cleanup;
+		giterr_set(GITERR_OS, "Failed to set attributes for file at '%s'", file->path_lock);
+		goto on_error;
 	}
 
 	p_unlink(file->path_original);
 
-	error = p_rename(file->path_lock, file->path_original);
+	if (p_rename(file->path_lock, file->path_original) < 0) {
+		giterr_set(GITERR_OS, "Failed to rename lockfile to '%s'", file->path_original);
+		goto on_error;
+	}
 
-cleanup:
 	git_filebuf_cleanup(file);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to commit locked file from buffer");
-	return GIT_SUCCESS;
+	return 0;
+
+on_error:
+	git_filebuf_cleanup(file);
+	return -1;
 }
 
 GIT_INLINE(void) add_to_cache(git_filebuf *file, const void *buf, size_t len)
@@ -299,22 +337,22 @@ GIT_INLINE(void) add_to_cache(git_filebuf *file, const void *buf, size_t len)
 
 int git_filebuf_write(git_filebuf *file, const void *buff, size_t len)
 {
-	int error;
 	const unsigned char *buf = buff;
 
+	ENSURE_BUF_OK(file);
+
 	for (;;) {
 		size_t space_left = file->buf_size - file->buf_pos;
 
 		/* cache if it's small */
 		if (space_left > len) {
 			add_to_cache(file, buf, len);
-			return GIT_SUCCESS;
+			return 0;
 		}
 
 		add_to_cache(file, buf, space_left);
-
-		if ((error = flush_buffer(file)) < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to write to buffer");
+		if (flush_buffer(file) < 0)
+			return -1;
 
 		len -= space_left;
 		buf += space_left;
@@ -323,32 +361,37 @@ int git_filebuf_write(git_filebuf *file, const void *buff, size_t len)
 
 int git_filebuf_reserve(git_filebuf *file, void **buffer, size_t len)
 {
-	int error;
 	size_t space_left = file->buf_size - file->buf_pos;
 
 	*buffer = NULL;
 
-	if (len > file->buf_size)
-		return GIT_ENOMEM;
+	ENSURE_BUF_OK(file);
+
+	if (len > file->buf_size) {
+		file->last_error = BUFERR_MEM;
+		return -1;
+	}
 
 	if (space_left <= len) {
-		if ((error = flush_buffer(file)) < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to reserve buffer");
+		if (flush_buffer(file) < 0)
+			return -1;
 	}
 
 	*buffer = (file->buffer + file->buf_pos);
 	file->buf_pos += len;
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_filebuf_printf(git_filebuf *file, const char *format, ...)
 {
 	va_list arglist;
 	size_t space_left;
-	int len, error;
+	int len, res;
 	char *tmp_buffer;
 
+	ENSURE_BUF_OK(file);
+
 	space_left = file->buf_size - file->buf_pos;
 
 	do {
@@ -356,24 +399,28 @@ int git_filebuf_printf(git_filebuf *file, const char *format, ...)
 		len = p_vsnprintf((char *)file->buffer + file->buf_pos, space_left, format, arglist);
 		va_end(arglist);
 
-		if (len < 0)
-			return git__throw(GIT_EOSERR, "Failed to format string");
+		if (len < 0) {
+			file->last_error = BUFERR_MEM;
+			return -1;
+		}
 
 		if ((size_t)len + 1 <= space_left) {
 			file->buf_pos += len;
-			return GIT_SUCCESS;
+			return 0;
 		}
 
-		if ((error = flush_buffer(file)) < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to output to buffer");
+		if (flush_buffer(file) < 0)
+			return -1;
 
 		space_left = file->buf_size - file->buf_pos;
 
 	} while ((size_t)len + 1 <= space_left);
 
 	tmp_buffer = git__malloc(len + 1);
-	if (!tmp_buffer)
-		return GIT_ENOMEM;
+	if (!tmp_buffer) {
+		file->last_error = BUFERR_MEM;
+		return -1;
+	}
 
 	va_start(arglist, format);
 	len = p_vsnprintf(tmp_buffer, len + 1, format, arglist);
@@ -381,12 +428,13 @@ int git_filebuf_printf(git_filebuf *file, const char *format, ...)
 
 	if (len < 0) {
 		git__free(tmp_buffer);
-		return git__throw(GIT_EOSERR, "Failed to format string");
+		file->last_error = BUFERR_MEM;
+		return -1;
 	}
 
-	error = git_filebuf_write(file, tmp_buffer, len);
+	res = git_filebuf_write(file, tmp_buffer, len);
 	git__free(tmp_buffer);
 
-	return error;
+	return res;
 }
 

src/filebuf.h

@@ -40,25 +40,35 @@ struct git_filebuf {
 
 	size_t buf_size, buf_pos;
 	git_file fd;
+	int last_error;
 };
 
 typedef struct git_filebuf git_filebuf;
 
 #define GIT_FILEBUF_INIT {0}
 
-/* The git_filebuf object lifecycle is:
+/*
+ * The git_filebuf object lifecycle is:
  * - Allocate git_filebuf, preferably using GIT_FILEBUF_INIT.
+ *
  * - Call git_filebuf_open() to initialize the filebuf for use.
+ *
  * - Make as many calls to git_filebuf_write(), git_filebuf_printf(),
- *   git_filebuf_reserve() as you like.
+ *   git_filebuf_reserve() as you like. The error codes for these
+ *   functions don't need to be checked. They are stored internally
+ *   by the file buffer.
+ *
  * - While you are writing, you may call git_filebuf_hash() to get
- *   the hash of all you have written so far.
+ *   the hash of all you have written so far. This function will
+ *   fail if any of the previous writes to the buffer failed.
+ *
  * - To close the git_filebuf, you may call git_filebuf_commit() or
  *   git_filebuf_commit_at() to save the file, or
  *   git_filebuf_cleanup() to abandon the file.  All of these will
- *   clear the git_filebuf object.
+ *   free the git_filebuf object. Likewise, all of these will fail
+ *   if any of the previous writes to the buffer failed, and set
+ *   an error code accordingly.
  */
-
 int git_filebuf_write(git_filebuf *lock, const void *buff, size_t len);
 int git_filebuf_reserve(git_filebuf *file, void **buff, size_t len);
 int git_filebuf_printf(git_filebuf *file, const char *format, ...) GIT_FORMAT_PRINTF(2, 3);

src/hashtable.c

@@ -227,11 +227,11 @@ int git_hashtable_remove2(git_hashtable *self, const void *key, void **old_value
 			node->key = NULL;
 			node->value = NULL;
 			self->key_count--;
-			return GIT_SUCCESS;
+			return 0;
 		}
 	}
 
-	return git__throw(GIT_ENOTFOUND, "Entry not found in hash table");
+	return GIT_ENOTFOUND;
 }
 
 int git_hashtable_merge(git_hashtable *self, git_hashtable *other)

src/posix.c

@@ -31,10 +31,9 @@ int p_getcwd(char *buffer_out, size_t size)
 	cwd_buffer = getcwd(buffer_out, size);
 
 	if (cwd_buffer == NULL)
-		return git__throw(GIT_EOSERR, "Failed to retrieve current working directory");
+		return -1;
 
 	git_path_mkposix(buffer_out);
-
 	git_path_string_to_dir(buffer_out, size);	//Ensure the path ends with a trailing slash
 
 	return GIT_SUCCESS;
@@ -44,14 +43,13 @@ int p_rename(const char *from, const char *to)
 {
 	if (!link(from, to)) {
 		p_unlink(from);
-		return GIT_SUCCESS;
+		return 0;
 	}
 
 	if (!rename(from, to))
-		return GIT_SUCCESS;
-
-	return GIT_ERROR;
+		return 0;
 
+	return -1;
 }
 
 #endif
@@ -64,7 +62,7 @@ int p_read(git_file fd, void *buf, size_t cnt)
 		if (r < 0) {
 			if (errno == EINTR || errno == EAGAIN)
 				continue;
-			return GIT_EOSERR;
+			return -1;
 		}
 		if (!r)
 			break;
@@ -82,14 +80,14 @@ int p_write(git_file fd, const void *buf, size_t cnt)
 		if (r < 0) {
 			if (errno == EINTR || errno == EAGAIN)
 				continue;
-			return GIT_EOSERR;
+			return -1;
 		}
 		if (!r) {
 			errno = EPIPE;
-			return GIT_EOSERR;
+			return -1;
 		}
 		cnt -= r;
 		b += r;
 	}
-	return GIT_SUCCESS;
+	return 0;
 }

src/util.h

@@ -7,8 +7,6 @@
 #ifndef INCLUDE_util_h__
 #define INCLUDE_util_h__
 
-#include "git2/errors.h"
-
 #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
 #define bitsizeof(x) (CHAR_BIT * sizeof(x))
 #define MSB(x, bits) ((x) & (~0ULL << (bitsizeof(x) - (bits))))
@@ -24,24 +22,21 @@
 GIT_INLINE(void *) git__malloc(size_t len)
 {
 	void *ptr = malloc(len);
-	if (!ptr)
-		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to allocate %d bytes.", (int)len);
+	if (!ptr) giterr_set_oom();
 	return ptr;
 }
 
 GIT_INLINE(void *) git__calloc(size_t nelem, size_t elsize)
 {
 	void *ptr = calloc(nelem, elsize);
-	if (!ptr)
-		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to allocate %d bytes.", (int)nelem*elsize);
+	if (!ptr) giterr_set_oom();
 	return ptr;
 }
 
 GIT_INLINE(char *) git__strdup(const char *str)
 {
 	char *ptr = strdup(str);
-	if (!ptr)
-		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to duplicate string");
+	if (!ptr) giterr_set_oom();
 	return ptr;
 }
 
@@ -56,7 +51,7 @@ GIT_INLINE(char *) git__strndup(const char *str, size_t n)
 
 	ptr = (char*)malloc(length + 1);
 	if (!ptr) {
-		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to duplicate string");
+		giterr_set_oom();
 		return NULL;
 	}
 
@@ -69,8 +64,7 @@ GIT_INLINE(char *) git__strndup(const char *str, size_t n)
 GIT_INLINE(void *) git__realloc(void *ptr, size_t size)
 {
 	void *new_ptr = realloc(ptr, size);
-	if (!new_ptr)
-		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to allocate %d bytes.", (int)size);
+	if (!new_ptr) giterr_set_oom();
 	return new_ptr;
 }