Want to help D compiler development: Two possible weekend projects

[David Nadlinger]

Hi all,

in case you have an afternoon or two to spare, here are two ideas 
how you could help with D compiler development (DMD/GDC/LDC):


  1) Provide an Open Source clean-room implementation of 
response_expand, the function the DMD frontend uses to parse 
response files. Unfortunately, it is under the copyright belongs 
(partly?) to Symantec, so Walter can't simply re-license it for 
use in GDC/LDC, where it is needed to provide DMD compatibility 
(gdmd/ldmd). For the full discussion, see: 
http://forum.dlang.org/thread/kdce69%24303k%241@digitalmars.com


  2) Write an ABI fuzzer: The C ABI can be quite complex to 
implement on some systems, notably x86_64 Posixen (i.e. the AMD64 
System V ABI). There has been a number of issues in the past (see 
e.g. the infamous 
http://d.puremagic.com/issues/show_bug.cgi?id=5570), but while 
most of the cases frequently occurring in common C APIs are 
handled correctly now, there are still a number of issues 
remaining.

What makes working on the related compiler code annoying, at 
least for me, is that test cases are few - bugs comings from ABI 
issues are hard to track down for most non-compiler people - and 
cumbersome to write/build manually, as you need to integrate the 
D part with another one compiler by the host C compiler.

Thus, the idea is to write a tool which randomly generates 
function prototypes and creates both C and D 'caller' and 
'callee' functions with that signature. The caller supplies a 
defined value for each parameter, and the callee in the 
respective other language checks if it was passed correctly. Same 
in the other direction for the return value.

The tool then compiles the files, links them together, and 
executes the test case. It will be beneficial for throughput to 
batch multiple function pairs together into one pair of source 
files. If any check fails, the test executable returns with an 
error code (or a segfault, ...), causing the fuzzer to save away 
the offending test case. If not, the next set of tests will be 
generated, and so on.

It might make sense to bias the parameter type generator towards 
"complex" types containing unions, packed structs, varargs, etc. 
In any case, it should be able to find issues on x86_64 in the 
latest released versions of both DMD (3-byte structs) and LDC 
(small structs passed as varargs when there are still registers 
available).


David