On Sat, Mar 3, 2012 at 00:35, FX <fxcoud...@gmail.com> wrote:
> Hi all,
> I'll offer my first patch to the new 4.8 trunk. I noticed that the 
> -fbacktrace option and the GFORTRAN_ERROR_BACKTRACE environment variable are 
> somewhat inconsistently handled. Currently, the environment variabled doesn't 
> actually override the compilation option, as it should. So, I set to change 
> that (checking both options.backtrace and compile_options.backtrace instead 
> of only the latter) when I realized that we could improve this further by 
> moving the checking code: it is currently located in the set_options() 
> function, which is called from the main Fortran routine (call generated by 
> the front-end). This means that it's not triggered if the main program is C.

Good catch!

> Full disclosure: I removed the function maybe_find_addr2line() because it's 
> not needed anymore now the code was regrouped. However, I'll note that I 
> don't understand why it was useful before, and that I think the comment on 
> top of it was wrong (variable "options" could be seen in the function, it was 
> just shadowed by the local function argument!). Thus, while I was at it, I 
> renamed the options argument to set_options(), just to make sure we didn't 
> have a problem of this sort in the future.

I added it because, as you say, the argument "options" in
set_options() prevented access to the global variable options, and I
was lazy and considered a new function faster than renaming the
argument. :)

> The change was bootstrapped and regtested on x86_64-apple-darwin11, but is an 
> area not covered by the testsuite. I have manually checked that running 
> various types of abort, both in a pure Fortran code and a mixed C/Fortran 
> (with C main), with all combinations -fno-backtrace/GFORTRAN_ERROR_BACKTRACE, 
> behaved as expected.

I don't think it will work if you have a C main program which then
calls _gfortran_set_options() to enable backtracing per the
mixed-language programming chapter in the manual. You probably need to
move the setup code to a separate function which is called both from
init and set_options.

Also, in the patch as it stands now, you could make find_addr2line
static and remove the prototype from libgfortran.h.  That being said,
I'd recommend moving both find_addr2line and the signal handler setup
code to backtrace.c, and then do a bit of janitorial work checking
which functions and variables can be made static.

Janne Blomqvist

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