11672 2017-06-15 18:41:11 +0000 gcc 7 format-truncation off by one with O2 2018-05-10 08:01:50 +0000 1 1 7 Build System, Metadata & Runtime OE-Core devtools / tool chain unspecified x86 Multiple RESOLVED FIXED Medium+ normal 2.5 M4 1 mark.asselstine raj.khem mark.hatle meta.mr.watcher meta.watcher raj.khem richard.purdie --- --- No (bug/feature does not impact docs) oldest_to_newest 74246 0 3823 mark.asselstine 2017-06-15 18:41:11 +0000 Created attachment 3823 example C file If you have a program such as --- #include <stdio.h> int main(int argc, char **argv) { int i = 0; char buffer[100]; for(i=0; i <= 999; i++) snprintf(buffer, 5, "-%d", i); return 0; } --- and build it with something like: x86_64-overc-linux-gcc --sysroot=/home/mark/build/overc/tmp/work/core2-64-overc-linux/lxc/2.0.8-r0/recipe-sysroot -Wall -Werror -m64 -march=core2 -mtune=core2 -msse3 -mfpmath=sse -fPIC -DPIC -O2 -c range.c -o range where x86_64-overc-linux-gcc --version x86_64-overc-linux-gcc (GCC) 7.1.0 You will get --- range.c: In function 'main': range.c:10:25: error: 'snprintf' output may be truncated before the last format character [-Werror=format-truncation=] snprintf(buffer, 5, "-%d", i); ^~~~~ range.c:10:5: note: 'snprintf' output between 3 and 6 bytes into a destination of size 5 snprintf(buffer, 5, "-%d", i); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors --- NOTE that to my surprise the check is not using the type size (which would be 12 -- 10 chars in an int, plus sign, plus null). It is in fact using the loop logic to determine range but incorrectly using 1000 even though the loop stops at 999. Attached is a more extensive example which can be played with. 74248 1 mark.asselstine 2017-06-15 18:48:03 +0000 This seems to be reported to gcc already as https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78969 NOTE they even note the issue in LXC which is where I ran into this. 75907 2 raj.khem 2017-08-16 16:26:08 +0000 This missed the 7.2 gcc release. I dont see it getting fixed by 2.4 release. Therefore moving it to 2.5 80545 3 richard.purdie 2018-05-10 08:01:50 +0000 We now have gcc 7.3 everywhere including the stable branches which resolves this. 3823 2017-06-15 18:41:11 +0000 2017-06-15 18:41:11 +0000 example C file range.c text/x-csrc 1302 mark.asselstine LyoKeDg2XzY0LW92ZXJjLWxpbnV4LWdjYyAtLXN5c3Jvb3Q9L2hvbWUvbWFyay9idWlsZC9vdmVy Yy90bXAvd29yay9jb3JlMi02NC1vdmVyYy1saW51eC9seGMvMi4wLjgtcjAvcmVjaXBlLXN5c3Jv b3QgLVdhbGwgLVdlcnJvciAtbTY0IC1tYXJjaD1jb3JlMiAtbXR1bmU9Y29yZTIgLW1zc2UzIC1t ZnBtYXRoPXNzZSAtZlBJQyAtRFBJQyAtTzIgLWMgcmFuZ2UuYyAtbyByYW5nZQoKSSBhbSBzZWVp bmcgdGhlIGZvbGxvd2luZzoKLS0tCnJhbmdlLmM6IEluIGZ1bmN0aW9uICdtYWluJzoKcmFuZ2Uu YzozNjoyNTogZXJyb3I6ICdzbnByaW50Zicgb3V0cHV0IG1heSBiZSB0cnVuY2F0ZWQgYmVmb3Jl IHRoZSBsYXN0IGZvcm1hdCBjaGFyYWN0ZXIgWy1XZXJyb3I9Zm9ybWF0LXRydW5jYXRpb249XQog ICAgIHNucHJpbnRmKGJ1ZmZlciwgNSwgIi0lZCIsIGkpOwogICAgICAgICAgICAgICAgICAgICAg ICAgXn5+fn4KcmFuZ2UuYzozNjo1OiBub3RlOiAnc25wcmludGYnIG91dHB1dCBiZXR3ZWVuIDMg YW5kIDYgYnl0ZXMgaW50byBhIGRlc3RpbmF0aW9uIG9mIHNpemUgNQogICAgIHNucHJpbnRmKGJ1 ZmZlciwgNSwgIi0lZCIsIGkpOwogICAgIF5+fn5+fn5+fn5+fn5+fn5+fn5+fn5+fn5+fn5+CnJh bmdlLmM6NDQ6MjU6IGVycm9yOiAnc25wcmludGYnIG91dHB1dCBtYXkgYmUgdHJ1bmNhdGVkIGJl Zm9yZSB0aGUgbGFzdCBmb3JtYXQgY2hhcmFjdGVyIFstV2Vycm9yPWZvcm1hdC10cnVuY2F0aW9u PV0KICAgICBzbnByaW50ZihidWZmZXIsIDUsICItJWQiLCBpKTsKICAgICAgICAgICAgICAgICAg ICAgICAgIF5+fn5+CnJhbmdlLmM6NDQ6NTogbm90ZTogJ3NucHJpbnRmJyBvdXRwdXQgYmV0d2Vl biAzIGFuZCA2IGJ5dGVzIGludG8gYSBkZXN0aW5hdGlvbiBvZiBzaXplIDUKICAgICBzbnByaW50 ZihidWZmZXIsIDUsICItJWQiLCBpKTsKICAgICBefn5+fn5+fn5+fn5+fn5+fn5+fn5+fn5+fn5+ fgpjYzE6IGFsbCB3YXJuaW5ncyBiZWluZyB0cmVhdGVkIGFzIGVycm9ycwoKKi8KI2luY2x1ZGUg PHN0ZGlvLmg+CgppbnQgbWFpbihpbnQgYXJnYywgY2hhciAqKmFyZ3YpCnsKICBpbnQgaSA9IDA7 CiAgY2hhciBidWZmZXJbMTAwXTsKCiAgZm9yKGk9MDsgaSA8PSA5OTk7IGkrKykKICAgIHNucHJp bnRmKGJ1ZmZlciwgNSwgIi0lZCIsIGkpOwoKICBpID0gMDsKYWdhaW46CiAgaWYgKGkgPT0gMTAw MCkKICAgIGdvdG8gZXhpdDsKCiAgaWYgKGkpCiAgICBzbnByaW50ZihidWZmZXIsIDUsICItJWQi LCBpKTsKICBpKys7CiAgZ290byBhZ2FpbjsKCmV4aXQ6CiAgcmV0dXJuIDA7Cn0K