Re: Alternative to __FILE__/__LINE__

["François Dumont" <frs.dumont@gmail.com>]

On 04/03/2018 21:55, Marc Glisse wrote:
> On Sun, 4 Mar 2018, François Dumont wrote:
>
>>     Debug mode is using __FILE__/__LINE__ to show where the assertion 
>> took place. So assertion looks like this:
>>
>> /home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/deque:175: 
>>
>> Error: function requires a valid iterator range [__first, __last).
>>
>>     But IMHO a smarter information would be to provide the file:line 
>> in the source code that generated this assertion so that users could 
>> more easily go to the faulty code.
>
> How about printing a backtrace then? Though at some point the user 
> might want to start a debugger to get more information.
>
I eventually made use of __PRETTY_FUNCTION__ and glibc backtrace 
function which is already used by the profile mode.

With all those additional info debug assertions are much clearer and 
easier to detect in code. For instance:

/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/deque:175:
In function:
     void std::__debug::deque<_Tp, _Allocator>::assign(_InputIterator,
     _InputIterator) [with _InputIterator = const int*;
     <template-parameter-2-2> = void; _Tp = int; _Allocator =
     std::allocator<int>]

Backtrace:
     ./assign1_neg.exe() [0x4046b8]
     ./assign1_neg.exe() [0x400f19]
     /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0) 
[0x7fc7a12f3830]
     ./assign1_neg.exe() [0x400f79]

Error: function requires a valid iterator range [__first, __last).

Objects involved in the operation:
     iterator "__first" @ 0x0x7ffd79799140 {
       type = int const* (constant iterator);
     }
     iterator "__last" @ 0x0x7ffd79799148 {
       type = int const* (constant iterator);
     }

And with the help of the addr2line tool you can easily find where faulty 
code it.

I'll commit that once back in stage 1.

François