MPS issue job003758

TitleThe MPS does not build with gcc -Wconversion
Assigned userGareth Rees
DescriptionLots of projects have -Wconversion in their compilation options, for example [1]. But the MPS does not compile under gcc with this option. (See job003757 for the corresponding issue with respect to clang.)
AnalysisThe MPS is very clean as regards implicit integer conversions. The main problem encountered was bitfields. To convince GCC that there will be no data loss when assigning to a bitfield, you have to write:

    struct.field = ((type)value & (type)mask);

I encapsulated this in a macro in misc.h:

    #define BITFIELD(type, value, width) ((type)value & (((type)1 << (width)) - 1))

and then revised setter macros SegSetPM, SegSetDepth and so on to use it.

The other problem is that the event system uses the type int : 1 for Boolean bitfields. Because int is signed, the values of this type are 0 and -1, and so you can't assign TRUE to this bitfield (even using the BITFIELD macro) without getting a warning about the sign conversion. So I changed the type of these bitfields to unsigned : 1.
How foundmanual_test
Evidence[1] <>
Created byGareth Rees
Created on2014-04-11 14:24:20
Last modified byGareth Rees
Last modified on2014-04-14 21:50:22
History2014-04-11 GDR Created.


Change Effect Date User Description
185467 open 2014-04-11 15:28:03 Gareth Rees Turn -Wconversion off again. (The MPS builds with this option with gcc 4.8 but not with gcc 4.6.3 on the Travis buildbots.)
185463 open 2014-04-11 14:25:15 Gareth Rees Add -Wconversion to the options for GCC. Ensure that the MPS builds.
185459 open 2014-04-11 12:17:39 Gareth Rees Not ready for gcc -Wconversion.
185457 open 2014-04-11 12:06:28 Gareth Rees Add -Wconversion to options for GCC and Clang.
Ensure that the MPS builds with this option with Clang.