[Bug c/72797] bogus -Wmisleading-indentation with -ftrack-macro-expansion=0 on a multi-statement macro

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72797

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |manu at gcc dot gnu.org

--- Comment #1 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #0)
> When invoked with the -ftrack-macro-expansion=0 and
> -Wmisleading-indentation, GCC warns on the following program derived from a
> GCC test suite.  Since the code is clearly indented and there is no mention
> of the -ftrack-macro-expansion option having this effect, the warning is
> unexpected.

No mention where? Some diagnostics rely on macro info to produce better
diagnostics. If you deactivate it, then you get bad diagnostics. Don't do that.

> In addition, the documentation for -ftrack-macro-expansion=level says that 
> 
>   Value '0' of level de-activates this option just as if no
> -ftrack-macro-expansion was present on the command line. 
> 
> Contrary to the statement above, GCC output changes and the warning
> disappears when the -ftrack-macro-expansion option is removed.

Yes, this must be a relic of the time it was not the default.

Personally, I think we should get rid of this option. This was useful when
tracking macro expansion was new and to work-around bugs. There is no point in
maintaining two code paths and much less on trying to make diagnostics better
for the -ftrack-macro-expansion=0 path. That effort would be better spent in
making the default more efficient and useful.

If we give a warning for:

do { if (i) i = 0; i++; } while (0);

that is, the processed source, that would be different. But it doesn't seem to
be the case in 7.0