Commit 1e9b65bb authored by Markus Armbruster's avatar Markus Armbruster
Browse files

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: default avatarMarkus Armbruster <armbru@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Acked-by: default avatarLaszlo Ersek <lersek@redhat.com>
parent edf6f3b3

include/qapi/error.h

+34 −9
Original line number Diff line number Diff line
@@ -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.

qga/vss-win32.c

+1 −1
Original line number Diff line number Diff line
@@ -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,

    };

qga/vss-win32/requester.cpp

+3 −2
Original line number Diff line number Diff line
@@ -24,7 +24,8 @@ 
#define VSS_TIMEOUT_EVENT_MSEC 10



#define err_set(e, err, fmt, ...)                                       \

    ((e)->error_setg_win32((e)->errp, err, fmt, ## __VA_ARGS__))

    ((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 */

qga/vss-win32/requester.h

+4 −2
Original line number Diff line number Diff line
@@ -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 */

util/error.c

+39 −16
Original line number Diff line number Diff line
@@ -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) {