[committed] libstdc++: Replace operator>>(istream&, char*) [LWG 2499]

[Jonathan Wakely]

On 06/08/20 12:45 -0600, Martin Sebor via Libstdc++ wrote:
>On 8/6/20 10:00 AM, Jonathan Wakely wrote:
>>On 06/08/20 09:17 -0600, Martin Sebor via Libstdc++ wrote:
>>>Sorry.  I don't see this exercise as a complete waste of time
>>>(but I understand why it feels like that to you).
>>>
>>>What it highlights is the fact that the warning infrastructure
>>>we have in place is far from optimal for C++ in general (with
>>>its heavy reliance on ilining and templates) and the standard
>>>library in particular (especially with -Wno-system-headers).
>>>We should make an effort to do better.
>>>
>>>Setting aside the effort to clean up the library so that it can
>>>be used even with -Wsystem-headers,
>>
>>Yeah, it's an ongoing effort.
>>
>>>warnings about out of bounds
>>>accesses should trigger even with -Wno-system-headers.  If one
>>>doesn't I'd tend to view it as a bug.
>>
>>I agree. And __attribute__((__warning__(""))) too.
>
>I've opened four bugs to track some of the issues we've discussed:
>96502, 96503, and 96505 for the lost attribute effect after
>inlining, and 96508 for the system header interaction.  I wasn't
>able to reproduce the problem you're having with the attribute
>(calling an out-of-line function declared in a system header
>does produce a warning) so if you're not completely put off
>by your experience so far please take a look at it and see
>what I may have missed.

This preprocessed code fails to warn without -Wsystem-headers:

# 1 "user.C"
# 1 "sys.h" 1

# 2 "sys.h" 3


# 3 "sys.h" 3
__attribute__((warning("badness")))
void diagnose_badness();

template<typename T>
void foo(T t)
{
   if (t < 0)
     diagnose_badness();
}
# 2 "user.C" 2


# 3 "user.C"
int main()
{
   int i = -1;
   foo(i);
}