On 8 November 2019 17:57:51 CET, Martin Sebor <mse...@gmail.com> wrote: >On 11/6/19 2:06 PM, Martin Sebor wrote: >> On 11/6/19 1:39 PM, Jeff Law wrote: >>> On 11/6/19 1:27 PM, Martin Sebor wrote: >>>> On 11/6/19 11:55 AM, Jeff Law wrote: >>>>> On 11/6/19 11:00 AM, Martin Sebor wrote: >>>>>> The -Wstringop-overflow warnings for single-byte and multi-byte >>>>>> stores mention the amount of data being stored and the amount of >>>>>> space remaining in the destination, such as: >>>>>> >>>>>> >warning: writing 4 bytes into a region of size 0 [-Wstringop-overflow=] > >>>>>> >>>>>> 123 | *p = 0; >>>>>> | ~~~^~~ >>>>>> note: destination object declared here >>>>>> 45 | char b[N]; >>>>>> | ^ >>>>>> >>>>>> >A warning like this can take some time to analyze. First, the size >>>>>> >of the destination isn't mentioned and may not be easy to tell from >>>>>> the sources. In the note above, when N's value is the result of >>>>>> >some non-trivial computation, chasing it down may be a small project >>>>>> >in and of itself. Second, it's also not clear why the region size >>>>>> is zero. It could be because the offset is exactly N, or because >>>>>> it's negative, or because it's in some range greater than N. >>>>>> >>>>>> Mentioning both the size of the destination object and the offset >>>>>> >makes the existing messages clearer, are will become essential when >>>>>> GCC starts diagnosing overflow into allocated buffers (as my >>>>>> follow-on patch does). >>>>>> >>>>>> The attached patch enhances -Wstringop-overflow to do this by >>>>>> letting compute_objsize return the offset to its caller, doing >>>>>> something similar in get_stridx, and adding a new function to >>>>>> the strlen pass to issue this enhanced warning (eventually, I'd >>>>>> like the function to replace the -Wstringop-overflow handler in >>>>>> >builtins.c). With the change, the note above might read something >>>>>> like: >>>>>> >>>>>> note: at offset 11 to object ‘b’ with size 8 declared here >>>>>> 45 | char b[N]; >>>>>> | ^ >>>>>>
Is "to object" correct? Into? I somehow fund it hard to read as proposed. thanks,
