Re: [Tinycc-devel] [patch] adding path resolution to #line directives

[Michael Matz]

Hey,

On Thu, 5 May 2022, Raul Hernandez wrote:

> The code we generate looks something like this:
>
>     #line 29
> "../../../../../../home/spaceface/git/v/v/vlib/builtin/builtin.c.v"

It would seem better to canonicalize during generating this, because the 
above ...

>    /tmp/v_1000/../../../../../../home/spaceface/git/v/v/vlib/builtin/builtin.c
> .v:53: at panic_debug: Backtrace

... and this don't look equivalent anyway (they are equivalent only when 
the above relative path is less that seven levels deep from /).

>     @@ -2042,6 +2042,22 @@ include_done:
>                     pstrcpy(buf, sizeof buf, file->true_filename);
>                     *tcc_basename(buf) = 0;
>                     pstrcat(buf, sizeof buf, (char *)tokc.str.data);
>     +                // collapse relative `../`s
>     +                while ((q = strstr(buf, "../")) != NULL) {
>     +                    (q == buf) ? (*q = '\0') : (*(q-1) = '\0');
>     +                    last_slash = strrchr(buf, '/');
>     +                    if (last_slash == NULL) {
>     +                        memmove(buf, q + 2, strlen(q + 2) + 1);

So you simply remove '../' components without a matching directory part. 
That isn't correct in all circumstances.  You might consider using 
realpath(3) (which is in POSIX) to do all of this for you.  But as said, 
you might also be better off to just do that during generating the #line 
directives, so as to be independend of compiler behaviour.

> Would you be willing to merge something this?
>
> We’ve also added a function that returns the backtrace as a char** rather
> than printing it out,

This might be generally usefull to libtcc users, and the variant printing 
it out can be written in terms of the char** variant; so that seems 
sensible to have.

> and modified the backtrace functions to replace
> e.g. main__foo with main.foo in symbol names,

But this is quite specific to V, so not too applicable without making it 
more general, at which point it doesn't look too attractive anymore.


Ciao,
Michael.