diff options
| author | Eric Blake <eblake@redhat.com> | 2017-07-17 10:13:34 -0500 |
|---|---|---|
| committer | Gerd Hoffmann <kraxel@redhat.com> | 2017-07-20 10:02:11 +0200 |
| commit | 121829cb2160e9cd82482c1542699fa589688106 (patch) | |
| tree | e992c577f8777d07c634b08c5df68a2b08d24d15 /hw | |
| parent | d4e59218ab80e86015753782fb5378767a51ccd0 (diff) | |
usb: Fix build with newer gcc
gcc 7 is pickier about our sources:
hw/usb/bus.c: In function ‘usb_port_location’:
hw/usb/bus.c:410:66: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size between 0 and 15 [-Werror=format-truncation=]
snprintf(downstream->path, sizeof(downstream->path), "%s.%d",
^~
hw/usb/bus.c:410:9: note: ‘snprintf’ output between 3 and 28 bytes into a destination of size 16
snprintf(downstream->path, sizeof(downstream->path), "%s.%d",
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
upstream->path, portnr);
~~~~~~~~~~~~~~~~~~~~~~~
But we know that there are at most 5 levels of USB hubs, with at
most two digits per level; that plus the separating dots means we
use at most 15 bytes (including trailing NUL) of our 16-byte field.
Adding an assertion to show gcc that we checked for truncation is
enough to shut up the false-positive warning.
Inspired by an idea by Dr. David Alan Gilbert <dgilbert@redhat.com>.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20170717151334.17954-1-eblake@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Diffstat (limited to 'hw')
| -rw-r--r-- | hw/usb/bus.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/hw/usb/bus.c b/hw/usb/bus.c index 5939b273b9..d910f849e7 100644 --- a/hw/usb/bus.c +++ b/hw/usb/bus.c @@ -407,8 +407,10 @@ void usb_register_companion(const char *masterbus, USBPort *ports[], void usb_port_location(USBPort *downstream, USBPort *upstream, int portnr) { if (upstream) { - snprintf(downstream->path, sizeof(downstream->path), "%s.%d", - upstream->path, portnr); + int l = snprintf(downstream->path, sizeof(downstream->path), "%s.%d", + upstream->path, portnr); + /* Max string is nn.nn.nn.nn.nn, which fits in 16 bytes */ + assert(l < sizeof(downstream->path)); downstream->hubcount = upstream->hubcount + 1; } else { snprintf(downstream->path, sizeof(downstream->path), "%d", portnr); |