[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] Convert hvmloader sprintf() into snprintf()
> -----Original Message----- > From: David Vrabel > Sent: 29 November 2011 13:57 > To: Paul Durrant > Cc: xen-devel@xxxxxxxxxxxxxxxxxxx > Subject: Re: [Xen-devel] [PATCH] Convert hvmloader sprintf() into > snprintf() > [snip] > > +static void __copy(void *arg, char c) > > { > > - **buf = c; > > - (*buf)++; > > + struct __copy_context *ctxt = arg; > > + > > + ctxt->emitted++; > > + > > + if (ctxt->remaining == 0) > > + return; > > + > > + *(ctxt->ptr++) = c; > > + --ctxt->remaining; > > } > > > > -int sprintf(char *buf, const char *fmt, ...) > > +int snprintf(char *buf, size_t size, const char *fmt, ...) > > { > > va_list ap; > > + struct __copy_context ctxt; > > + > > + ctxt.ptr = buf; > > + ctxt.emitted = 0; > > + ctxt.remaining = size; > > > > va_start(ap, fmt); > > - _doprint(__copy, &buf, fmt, ap); > > + _doprint(__copy, &ctxt, fmt, ap); > > va_end(ap); > > > > - *buf = '\0'; > > - return 0; > > + if (ctxt.remaining != 0) > > + *ctxt.ptr = '\0'; > > + > > + return ctxt.emitted; > > } > > This doesn't return the correct value according the C99. From the > snprintf() man page: > > "The functions snprintf() and vsnprintf() do not write more than > size bytes (including the trailing '\0'). If the output was > truncated due to this limit then the return value is the number of > characters (not including the trailing '\0') which would have been > written to the final string if enough space had been available. > Thus, a return value of size or more means that the output > was truncated." > Actually, reading the code again, it is correct isn't it? ctxt.emitted is bumped for every character emitted by _doprint() regardless of whether it makes it into the buffer or not so in an overflow case the value returned will be the number of characters which would have been written not including the nul terminator. Paul _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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