Commit 1f51470d authored by Markus Armbruster's avatar Markus Armbruster Committed by Anthony Liguori

Revert "qemu-char: Print strerror message on failure" and deps

The commit's purpose is laudable:

    The only way for chardev drivers to communicate an error was to
    return a NULL pointer, which resulted in an error message that
    said _that_ something went wrong, but not _why_.

It attempts to achieve it by changing the interface to return 0/-errno
and update qemu_chr_open_opts() to use strerror() to display a more
helpful error message.  Unfortunately, it has serious flaws:

1. Backends "socket" and "udp" return bogus error codes, because
qemu_chr_open_socket() and qemu_chr_open_udp() assume that
unix_listen_opts(), unix_connect_opts(), inet_listen_opts(),
inet_connect_opts() and inet_dgram_opts() fail with errno set
appropriately.  That assumption is wrong, and the commit turns
unspecific error messages into misleading error messages.  For

    $ qemu-system-x86_64 -nodefaults -vnc :0 -chardev socket,id=bar,host=xxx
    inet_connect: host and/or port not specified
    chardev: opening backend "socket" failed: No such file or directory

ENOENT is what happens to be in my errno when the backend returns
-errno.  Let's put ERANGE there just for giggles:

    $ qemu-system-x86_64 -nodefaults -vnc :0 -chardev socket,id=bar,host=xxx -drive if=none,iops=99999999999999999999
    inet_connect: host and/or port not specified
    chardev: opening backend "socket" failed: Numerical result out of range

Worse: when errno happens to be zero, return -errno erroneously
signals success, and qemu_chr_new_from_opts() dies dereferencing
uninitialized chr.  I observe this with "-serial unix:".

2. All qemu_chr_open_opts() knows about the error is an errno error
code.  That's simply not enough for a decent message.  For instance,
when inet_dgram() can't resolve the parameter host, which errno code
should it use?  What if it can't resolve parameter localaddr?

Clue: many backends already report errors in their open methods.
Let's revert the flawed commit along with its dependencies, and fix up
the silent error paths instead.

This reverts commit 6e1db57b.



This reverts commit aad04cd0.

The parts of commit db418a0a "Add stdio char device on windows" that
depend on the reverted change fixed up.
Signed-off-by: default avatarMarkus Armbruster <>
Signed-off-by: default avatarAnthony Liguori <>
parent f0cdc966
......@@ -1510,7 +1510,7 @@ static void text_console_do_init(CharDriverState *chr, DisplayState *ds)
int text_console_init(QemuOpts *opts, CharDriverState **_chr)
CharDriverState *text_console_init(QemuOpts *opts)
CharDriverState *chr;
TextConsole *s;
......@@ -1542,7 +1542,7 @@ int text_console_init(QemuOpts *opts, CharDriverState **_chr)
if (!s) {
return -EBUSY;
return NULL;
s->chr = chr;
......@@ -1550,9 +1550,7 @@ int text_console_init(QemuOpts *opts, CharDriverState **_chr)
s->g_height = height;
chr->opaque = s;
chr->chr_set_echo = text_console_set_echo;
*_chr = chr;
return 0;
return chr;
void text_consoles_set_display(DisplayState *ds)
......@@ -356,7 +356,7 @@ void vga_hw_text_update(console_ch_t *chardata);
int is_graphic_console(void);
int is_fixedsize_console(void);
int text_console_init(QemuOpts *opts, CharDriverState **_chr);
CharDriverState *text_console_init(QemuOpts *opts);
void text_consoles_set_display(DisplayState *ds);
void console_select(unsigned int index);
void console_color_init(DisplayState *ds);
......@@ -562,7 +562,7 @@ static void baum_close(struct CharDriverState *chr)
int chr_baum_init(QemuOpts *opts, CharDriverState **_chr)
CharDriverState *chr_baum_init(QemuOpts *opts)
BaumDriverState *baum;
CharDriverState *chr;
......@@ -614,8 +614,7 @@ int chr_baum_init(QemuOpts *opts, CharDriverState **_chr)
*_chr = chr;
return 0;
return chr;
......@@ -624,5 +623,5 @@ fail_handle:
return -EIO;
return NULL;
......@@ -23,4 +23,4 @@
/* char device */
int chr_baum_init(QemuOpts *opts, CharDriverState **_chr);
CharDriverState *chr_baum_init(QemuOpts *opts);
......@@ -64,7 +64,7 @@ static void msmouse_chr_close (struct CharDriverState *chr)
g_free (chr);
int qemu_chr_open_msmouse(QemuOpts *opts, CharDriverState **_chr)
CharDriverState *qemu_chr_open_msmouse(QemuOpts *opts)
CharDriverState *chr;
......@@ -74,6 +74,5 @@ int qemu_chr_open_msmouse(QemuOpts *opts, CharDriverState **_chr)
qemu_add_mouse_event_handler(msmouse_event, chr, 0, "QEMU Microsoft Mouse");
*_chr = chr;
return 0;
return chr;
/* msmouse.c */
int qemu_chr_open_msmouse(QemuOpts *opts, CharDriverState **_chr);
CharDriverState *qemu_chr_open_msmouse(QemuOpts *opts);
This diff is collapsed.
......@@ -188,7 +188,7 @@ static void print_allowed_subtypes(void)
fprintf(stderr, "\n");
int qemu_chr_open_spice(QemuOpts *opts, CharDriverState **_chr)
CharDriverState *qemu_chr_open_spice(QemuOpts *opts)
CharDriverState *chr;
SpiceCharDriver *s;
......@@ -200,7 +200,7 @@ int qemu_chr_open_spice(QemuOpts *opts, CharDriverState **_chr)
if (name == NULL) {
fprintf(stderr, "spice-qemu-char: missing name parameter\n");
return -EINVAL;
return NULL;
for(;*psubtype != NULL; ++psubtype) {
if (strcmp(name, *psubtype) == 0) {
......@@ -211,7 +211,7 @@ int qemu_chr_open_spice(QemuOpts *opts, CharDriverState **_chr)
if (subtype == NULL) {
fprintf(stderr, "spice-qemu-char: unsupported name\n");
return -EINVAL;
return NULL;
chr = g_malloc0(sizeof(CharDriverState));
......@@ -233,6 +233,5 @@ int qemu_chr_open_spice(QemuOpts *opts, CharDriverState **_chr)
*_chr = chr;
return 0;
return chr;
......@@ -45,7 +45,7 @@ int qemu_spice_migrate_info(const char *hostname, int port, int tls_port,
void do_info_spice_print(Monitor *mon, const QObject *data);
void do_info_spice(Monitor *mon, QObject **ret_data);
int qemu_chr_open_spice(QemuOpts *opts, CharDriverState **_chr);
CharDriverState *qemu_chr_open_spice(QemuOpts *opts);
#else /* CONFIG_SPICE */
#include "monitor.h"
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