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authorEric Blake <eblake@redhat.com>2017-07-17 10:13:34 -0500
committerGerd Hoffmann <kraxel@redhat.com>2017-07-20 10:02:11 +0200
commit121829cb2160e9cd82482c1542699fa589688106 (patch)
treee992c577f8777d07c634b08c5df68a2b08d24d15 /hw/usb
parentd4e59218ab80e86015753782fb5378767a51ccd0 (diff)
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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/usb')
-rw-r--r--hw/usb/bus.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/hw/usb/bus.c b/hw/usb/bus.c
index 5939b27..d910f84 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);