MELT plugin: test fopen

[Pierre Vittet <piervit at pvittet dot com>]

Hello,

I would like to present you a small plugin, which could be a good 
exemple of a MELT use case.
This plugin allows to monitor that after every call to the fopen 
function, we have a test on the pointer returned by fopen (monitoring 
that it is not null).

It creates a pass after SSA and works on gimple. It firstly matchs the 
gimple_call on fopen and save the tree corresponding to the FILE *. Then 
we check that the next instruction is a gimple_cond between the saved 
tree and the NULL ptr.
When no test are found, the following error is returned:
"test_fopen_cfile.c:35:11: warning: fopen not followed by a test on his 
returned pointer [enabled by default]"

I think MELT is particulary adaptated when we have to match tree or 
gimples like I do here.

For the moment I have only used it on small test file. I will try to see 
what it gives on a more realistic small to medium application.

The code can be find on github: https://github.com/Piervit/GMWarn . The 
idea is to add more plugins. If you have some ideas or remarks, I am 
interested (however I still have to learn a lot from both GCC and MELT).

If you try the code you will need to use the GCC MELT branch (or there 
is some changes to do in the Makefile to have it with MELT as plugin).


Regards!