Add an embryo of a TLS-aware error handling system

This adds the per-thread global variable git_errno to the
system, which callers can examine to get information about
an error.

Two helper functions are added to reduce LoC-count for the
library code itself.

Also, some exceptions are made for running sparse on GIT_TLS
definitions, since it doesn't grok thread-local variables at
all.

Signed-off-by: Andreas Ericsson <ae@op5.se>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Makefile

@@ -41,7 +41,7 @@ apidocs:
 test: $(TEST_RUN)
 
 sparse:
-	@for i in $(SRC_C); do sparse $$i $(SPARSE_FLAGS) $(BASIC_CFLAGS) $(CFLAGS); done
+	@for i in $(SRC_C); do sparse $$i -DSPARSE_IS_RUNNING $(SPARSE_FLAGS) $(BASIC_CFLAGS) $(CFLAGS); done
 
 install-headers: $(PUBLIC_HEADERS)
 	@mkdir -p /tmp/gitinc/git

src/common.h

@@ -3,6 +3,7 @@
 
 #include "cc-compat.h"
 #include "util.h"
+#include "errors.h"
 #include <errno.h>
 #include <stdlib.h>
 #include <unistd.h>

src/errors.c

@@ -0,0 +1,23 @@
+#include "common.h"
+#include "thread-utils.h" /* for GIT_TLS */
+
+/* compile-time constant initialization required */
+GIT_TLS int git_errno = 0;
+
+static struct {
+	int num;
+	const char *str;
+} error_codes[] = {
+	{ GIT_ENOTOID, "Not a git oid" },
+	{ GIT_ENOTFOUND, "Object does not exist in the scope searched" },
+};
+
+const char *git_strerror(int num)
+{
+	int i;
+	for (i = 0; i < ARRAY_SIZE(error_codes); i++)
+		if (num == error_codes[i].num)
+			return error_codes[i].str;
+
+	return "Unknown error";
+}

src/errors.h

@@ -0,0 +1,17 @@
+#ifndef INCLUDE_errors_h__
+#define INCLUDE_errors_h__
+#include "git/errors.h"
+
+/* convenience functions */
+static inline int git_int_error(int code)
+{
+	git_errno = code;
+	return code;
+}
+
+static inline void *git_ptr_error(int code)
+{
+	git_errno = code;
+	return NULL;
+}
+#endif

src/git/errors.h

@@ -0,0 +1,25 @@
+#ifndef INCLUDE_git_errors_h__
+#define INCLUDE_git_errors_h__
+/**
+ * @file git/errors.h
+ * @brief Git error handling routines and variables
+ * @ingroup Git
+ * @{
+ */
+
+#include "common.h"
+#include "thread-utils.h"
+GIT_BEGIN_DECL
+
+/** The git errno. */
+GIT_EXTERN(int) GIT_TLS git_errno;
+
+/**
+ * strerror() for the Git library
+ * @param num The error code to explain
+ * @return a string explaining the error code
+ */
+GIT_EXTERN(const char *) git_strerror(int num);
+/** @} */
+GIT_END_DECL
+#endif

src/git/thread-utils.h

@@ -22,4 +22,11 @@
 # define GIT_TLS /* nothing: tls vars are thread-global */
 #endif
 
+/* sparse doesn't grok thread-local variables */
+#ifdef SPARSE_IS_RUNNING
+# undef GIT_HAS_TLS
+# undef GIT_TLS
+# define GIT_TLS
+#endif
+
 #endif /* INCLUDE_git_thread_utils_h__ */