> On March 29, 2015, 9:11 p.m., Matt Jordan wrote: > > So, small problem with this change. When compiling with gcc 4.8.2, I get > > the following warning: > > > > In function ‘read’, > > inlined from ‘inotify_daemon’ at stdtime/localtime.c:380:6: > > /usr/include/x86_64-linux-gnu/bits/unistd.h:42:2: error: call to > > ‘__read_chk_warn’ declared with attribute warning: read called with bigger > > length than size of the destination buffer [-Werror] > > return __read_chk_warn (__fd, __buf, __nbytes, __bos0 (__buf)); > > > > > > Interestingly, the build agents didn't kick this back. But we'll need to > > find a way to get this fixed for gcc as well.
So, this is interesting. Looking at unistd.h: extern ssize_t __read_chk (int __fd, void *__buf, size_t __nbytes, size_t __buflen) __wur; extern ssize_t __REDIRECT (__read_alias, (int __fd, void *__buf, size_t __nbytes), read) __wur; extern ssize_t __REDIRECT (__read_chk_warn, (int __fd, void *__buf, size_t __nbytes, size_t __buflen), __read_chk) __wur __warnattr ("read called with bigger length than size of " "the destination buffer"); __fortify_function __wur ssize_t read (int __fd, void *__buf, size_t __nbytes) { if (__bos0 (__buf) != (size_t) -1) { if (!__builtin_constant_p (__nbytes)) return __read_chk (__fd, __buf, __nbytes, __bos0 (__buf)); if (__nbytes > __bos0 (__buf)) return __read_chk_warn (__fd, __buf, __nbytes, __bos0 (__buf)); } return __read_alias (__fd, __buf, __nbytes); } That is, if __nbytes is greater than the result of GCC's built-in object size (https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html) for the struct, we'll kick back a warning. As it turns out, this is because there is an error in the code here - we're passing the address of the pointer to the struct, not iev, which is a pointer to the struct. Hence, the number of bytes is probably going to be lot larger than the number of bytes that make up a pointer! Changing this to just read from the pointer to the struct fixes the warning. - Matt ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviewboard.asterisk.org/r/4530/#review14961 ----------------------------------------------------------- On March 29, 2015, 8:52 p.m., Diederik de Groot wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > https://reviewboard.asterisk.org/r/4530/ > ----------------------------------------------------------- > > (Updated March 29, 2015, 8:52 p.m.) > > > Review request for Asterisk Developers. > > > Bugs: ASTERISK-24917 > https://issues.asterisk.org/jira/browse/ASTERISK-24917 > > > Repository: Asterisk > > > Description > ------- > > clang's static analyzer will throw quite a number warnings / errors during > compilation, some of which can be very helpfull in finding corner-case > bugs\nclang compiler warning:-Wgnu-variable-sized-type-not-at-end > > > Diffs > ----- > > /branches/13/main/stdtime/localtime.c 433444 > > Diff: https://reviewboard.asterisk.org/r/4530/diff/ > > > Testing > ------- > > > Thanks, > > Diederik de Groot > >
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