RFE: support for capturing chains of macro expansions?

[davidmalcolm]

Addressing one specific point:

* Can you explain your question around macro expansion? SARIF defines a `originalUriBaseId` property for defining absolute paths for non-deterministic source roots, which you're already populating. Would you like other macro/var definitions to be expressed in the format?

...when I spoke of macro expansion, I was referring to languages with a preprocessor, such as C/C++, where the question of "where in the source-code-under-analysis are we?" can involve a nested series of macro expansions, potentially involving multiple files (e.g. use of a macro declared in one header, which refers to a macro in another header, etc).

Consider e.g.:

#include <stdlib.h>

#define FREE(X) free(X)
#define REALLY_FREE(X) FREE(X)
#define MAYBE_FREE(X,F) do { if (F) REALLY_FREE(X); } while (0)

void test (void *p, int flag)
{
  MAYBE_FREE(p, flag);
  MAYBE_FREE(p, flag);
}

GCC output: https://godbolt.org/z/87vf1cGKK

where GCC's textual output can emit the chain of macro expansions:

<source>: In function 'test':
<source>:3:17: warning: double-'free' of 'p' [CWE-415] [-Wanalyzer-double-free]
    3 | #define FREE(X) free(X)
      |                 ^~~~~~~
<source>:4:24: note: in expansion of macro 'FREE'
    4 | #define REALLY_FREE(X) FREE(X)
      |                        ^~~~
<source>:5:37: note: in expansion of macro 'REALLY_FREE'
    5 | #define MAYBE_FREE(X,F) do { if (F) REALLY_FREE(X); } while (0)
      |                                     ^~~~~~~~~~~
<source>:10:3: note: in expansion of macro 'MAYBE_FREE'
   10 |   MAYBE_FREE(p, flag);
      |   ^~~~~~~~~~

There didn't seem to be a way to express this within SARIF. Is there one, or did I miss it? Thanks!

Originally posted by @davidmalcolm in #531 (comment)

[davidmalcolm]

I wonder if this could be expressed by adding a new "kind" within locationRelationship's 3.34.3 kinds property, similar to how that can capture a chain of #include?

[sthagen]

I suggest to discuss this proposal in TC meeting 2024-08-08