Re: [PATCH 3/4] libbacktrace: work with aslr on windows

[Gabriel Ravier <gabravier@gmail.com>]

On 1/20/23 14:39, Eli Zaretskii via Gcc wrote:
>> From: Björn Schäpers <gcc@hazardy.de>
>> Date: Fri, 20 Jan 2023 11:54:08 +0100
>>
>> @@ -856,7 +870,12 @@ coff_add (struct backtrace_state *state, int descriptor,
>>   				  + (sections[i].offset - min_offset));
>>       }
>>   
>> -  if (!backtrace_dwarf_add (state, /* base_address */ 0, &dwarf_sections,
>> +#ifdef HAVE_WINDOWS_H
>> +    module_handle = (uintptr_t) GetModuleHandleW (NULL);
>> +    base_address = module_handle - image_base;
>> +#endif
>> +
>> +  if (!backtrace_dwarf_add (state, base_address, &dwarf_sections,
>>   			    0, /* FIXME: is_bigendian */
>>   			    NULL, /* altlink */
>>   			    error_callback, data, fileline_fn,
> Why do you force using the "wide" APIs here?  Won't GetModuleHandle do
> the job, whether it resolves to GetModuleHandleA or GetModuleHandleW?

I would expect the reason to be either that:

- using wide APIs with Windows is generally considered to be a best 
practice, even when not strictly needed (and in this case I can't see 
any problem with doing so, unless maybe we want to code to work with 
Windows 95 or something like that...)

- using the narrow API somehow has an actual drawback, for example maybe 
it might not work if the name of the exe file the NULL will tell it to 
get a handle to contains wide characters