[Interest] Qt 5 LTO build on OS X 10.9 (and earlier)

René J. V. Bertin rjvbertin at gmail.com
Sat Sep 12 00:19:27 CEST 2015

Thiago Macieira wrote:

> I have no clue what issues with debugging there might be. I haven't
> experienced that problem with GCC's LTO.

It's like debugging an application or library built without -g. Indeed, I 
haven't noticed any issue like that with gcc 5 on Linux.

>> Well, yes, it's something to do with the linker, but the end result is that
>> symbolic or source-level (or whatever you wish to call it) is possible or
                                                              ^ debugging 
>> not ...

> I don't see any reason why the compiler would get lost.

And I have no idea why you drag the compiler into this :)

My hunch is that the -g is dropped during the linking stage, it doesn't show in 
the ld arguments at least. The way I think of it is that LTO basically repeats 
part of the compilation or maybe just the assembly-level optimisation after 
loading all code that must be linked together. If that's done after dropping -g, 
that would explain the absence of debug information in the resulting binary.
(then again that might be as close to the truth as Genesis is :) )


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