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error: On abort, report where the error was created 

This is particularly useful when we abort in error_propagate(),
because there the stack backtrace doesn't lead to where the error was
created.  Looks like this:

    Unexpected error in parse_block_error_action() at .../qemu/blockdev.c:322:
    qemu-system-x86_64: -drive if=none,werror=foo: 'foo' invalid write error action
    Aborted (core dumped)

Note: to get this example output, I monkey-patched drive_new() to pass
&error_abort to blockdev_init().

To keep the error handling boiler plate from growing even more, all
error_setFOO() become macros expanding into error_setFOO_internal()
with additional __FILE__, __LINE__, __func__ arguments.  Not exactly
pretty, but it works.

The macro trickery breaks down when you take the address of an
error_setFOO().  Fortunately, we do that in just one place: qemu-ga's
Windows VSS provider and requester DLL wants to call
error_setg_win32() through a function pointer "to avoid linking glib
to the DLL".  Use error_setg_win32_internal() there.  The use of the
function pointer is already wrapped in a macro, so the churn isn't
bad.

Code size increases by some 35KiB for me (0.7%).  Tolerable.  Could be
less if we passed relative rather than absolute source file names to
the compiler, or forwent reporting __func__.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Markus Armbruster 2015-06-19 19:21:59 +02:00
parent edf6f3b335
commit 1e9b65bb1b
5 changed files with 81 additions and 30 deletions
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43
include/qapi/error.h
View File

@ -104,16 +104,26 @@ ErrorClass error_get_class(const Error *err);
* The new error's class is ERROR_CLASS_GENERIC_ERROR, and its
* human-readable error message is made from printf-style @fmt, ...
*/
void error_setg(Error **errp, const char *fmt, ...)
GCC_FMT_ATTR(2, 3);
#define error_setg(errp, fmt, ...) \
error_setg_internal((errp), __FILE__, __LINE__, __func__, \
(fmt), ## __VA_ARGS__)
void error_setg_internal(Error **errp,
const char *src, int line, const char *func,
const char *fmt, ...)
GCC_FMT_ATTR(5, 6);
/*
* Just like error_setg(), with @os_error info added to the message.
* If @os_error is non-zero, ": " + strerror(os_error) is appended to
* the human-readable error message.
*/
void error_setg_errno(Error **errp, int os_error, const char *fmt, ...)
GCC_FMT_ATTR(3, 4);
#define error_setg_errno(errp, os_error, fmt, ...) \
error_setg_errno_internal((errp), __FILE__, __LINE__, __func__, \
(os_error), (fmt), ## __VA_ARGS__)
void error_setg_errno_internal(Error **errp,
const char *fname, int line, const char *func,
int os_error, const char *fmt, ...)
GCC_FMT_ATTR(6, 7);
#ifdef _WIN32
/*
@ -121,8 +131,13 @@ void error_setg_errno(Error **errp, int os_error, const char *fmt, ...)
* If @win32_error is non-zero, ": " + g_win32_error_message(win32_err)
* is appended to the human-readable error message.
*/
void error_setg_win32(Error **errp, int win32_err, const char *fmt, ...)
GCC_FMT_ATTR(3, 4);
#define error_setg_win32(errp, win32_err, fmt, ...) \
error_setg_win32_internal((errp), __FILE__, __LINE__, __func__, \
(win32_err), (fmt), ## __VA_ARGS__)
void error_setg_win32_internal(Error **errp,
const char *src, int line, const char *func,
int win32_err, const char *fmt, ...)
GCC_FMT_ATTR(6, 7);
#endif
/*
@ -143,7 +158,12 @@ void error_propagate(Error **dst_errp, Error *local_err);
/*
* Convenience function to report open() failure.
*/
void error_setg_file_open(Error **errp, int os_errno, const char *filename);
#define error_setg_file_open(errp, os_errno, filename) \
error_setg_file_open_internal((errp), __FILE__, __LINE__, __func__, \
(os_errno), (filename))
void error_setg_file_open_internal(Error **errp,
const char *src, int line, const char *func,
int os_errno, const char *filename);
/*
* Return an exact copy of @err.
@ -166,8 +186,13 @@ void error_report_err(Error *);
* Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
* strongly discouraged.
*/
void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
GCC_FMT_ATTR(3, 4);
#define error_set(errp, err_class, fmt, ...) \
error_set_internal((errp), __FILE__, __LINE__, __func__, \
(err_class), (fmt), ## __VA_ARGS__)
void error_set_internal(Error **errp,
const char *src, int line, const char *func,
ErrorClass err_class, const char *fmt, ...)
GCC_FMT_ATTR(6, 7);
/*
* Pass to error_setg() & friends to abort() on error.

2
qga/vss-win32.c
View File

@ -150,7 +150,7 @@ void qga_vss_fsfreeze(int *nr_volume, Error **errp, bool freeze)
const char *func_name = freeze ? "requester_freeze" : "requester_thaw";
QGAVSSRequesterFunc func;
ErrorSet errset = {
.error_setg_win32 = error_setg_win32,
.error_setg_win32 = error_setg_win32_internal,
.errp = errp,
};

5
qga/vss-win32/requester.cpp
View File

@ -23,8 +23,9 @@
/* Call QueryStatus every 10 ms while waiting for frozen event */
#define VSS_TIMEOUT_EVENT_MSEC 10
#define err_set(e, err, fmt, ...) \
((e)->error_setg_win32((e)->errp, err, fmt, ## __VA_ARGS__))
#define err_set(e, err, fmt, ...) \
((e)->error_setg_win32((e)->errp, __FILE__, __LINE__, __func__, \
err, fmt, ## __VA_ARGS__))
/* Bad idea, works only when (e)->errp != NULL: */
#define err_is_set(e) ((e)->errp && *(e)->errp)
/* To lift this restriction, error_propagate(), like we do in QEMU code */

6
qga/vss-win32/requester.h
View File

@ -23,8 +23,10 @@ extern "C" {
struct Error;
/* Callback to set Error; used to avoid linking glib to the DLL */
typedef void (*ErrorSetFunc)(struct Error **errp, int win32_err,
const char *fmt, ...) GCC_FMT_ATTR(3, 4);
typedef void (*ErrorSetFunc)(struct Error **errp,
const char *src, int line, const char *func,
int win32_err, const char *fmt, ...)
GCC_FMT_ATTR(6, 7);
typedef struct ErrorSet {
ErrorSetFunc error_setg_win32;
struct Error **errp; /* restriction: must not be null */

55
util/error.c
View File

@ -18,12 +18,23 @@ struct Error
{
char *msg;
ErrorClass err_class;
const char *src, *func;
int line;
};
Error *error_abort;
static void error_setv(Error **errp, ErrorClass err_class,
const char *fmt, va_list ap)
static void error_do_abort(Error *err)
{
fprintf(stderr, "Unexpected error in %s() at %s:%d:\n",
err->func, err->src, err->line);
error_report_err(err);
abort();
}
static void error_setv(Error **errp,
const char *src, int line, const char *func,
ErrorClass err_class, const char *fmt, va_list ap)
{
Error *err;
int saved_errno = errno;
@ -36,10 +47,12 @@ static void error_setv(Error **errp, ErrorClass err_class,
err = g_malloc0(sizeof(*err));
err->msg = g_strdup_vprintf(fmt, ap);
err->err_class = err_class;
err->src = src;
err->line = line;
err->func = func;
if (errp == &error_abort) {
error_report_err(err);
abort();
error_do_abort(err);
}
*errp = err;
@ -47,25 +60,31 @@ static void error_setv(Error **errp, ErrorClass err_class,
errno = saved_errno;
}
void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
void error_set_internal(Error **errp,
const char *src, int line, const char *func,
ErrorClass err_class, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
error_setv(errp, err_class, fmt, ap);
error_setv(errp, src, line, func, err_class, fmt, ap);
va_end(ap);
}
void error_setg(Error **errp, const char *fmt, ...)
void error_setg_internal(Error **errp,
const char *src, int line, const char *func,
const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
error_setv(errp, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
error_setv(errp, src, line, func, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
va_end(ap);
}
void error_setg_errno(Error **errp, int os_errno, const char *fmt, ...)
void error_setg_errno_internal(Error **errp,
const char *src, int line, const char *func,
int os_errno, const char *fmt, ...)
{
va_list ap;
char *msg;
@ -76,7 +95,7 @@ void error_setg_errno(Error **errp, int os_errno, const char *fmt, ...)
}
va_start(ap, fmt);
error_setv(errp, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
error_setv(errp, src, line, func, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
va_end(ap);
if (os_errno != 0) {
@ -88,14 +107,19 @@ void error_setg_errno(Error **errp, int os_errno, const char *fmt, ...)
errno = saved_errno;
}
void error_setg_file_open(Error **errp, int os_errno, const char *filename)
void error_setg_file_open_internal(Error **errp,
const char *src, int line, const char *func,
int os_errno, const char *filename)
{
error_setg_errno(errp, os_errno, "Could not open '%s'", filename);
error_setg_errno_internal(errp, src, line, func, os_errno,
"Could not open '%s'", filename);
}
#ifdef _WIN32
void error_setg_win32(Error **errp, int win32_err, const char *fmt, ...)
void error_setg_win32_internal(Error **errp,
const char *src, int line, const char *func,
int win32_err, const char *fmt, ...)
{
va_list ap;
char *msg1, *msg2;
@ -105,7 +129,7 @@ void error_setg_win32(Error **errp, int win32_err, const char *fmt, ...)
}
va_start(ap, fmt);
error_setv(errp, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
error_setv(errp, src, line, func, ERROR_CLASS_GENERIC_ERROR, fmt, ap);
va_end(ap);
if (win32_err != 0) {
@ -158,8 +182,7 @@ void error_free(Error *err)
void error_propagate(Error **dst_errp, Error *local_err)
{
if (local_err && dst_errp == &error_abort) {
error_report_err(local_err);
abort();
error_do_abort(local_err);
} else if (dst_errp && !*dst_errp) {
*dst_errp = local_err;
} else if (local_err) {