| Title | Compilation of apss.c fails with GCC 6.1 |
| Status | closed |
| Priority | essential |
| Assigned user | Gareth Rees |
| Organization | Ravenbrook |
| Description | Basile Starynkevitch writes [1]: I just am trying to compile the latest MPS from git on a Linux/Debian/Testing system (kernel is 4.6, GNU libc is 2.23, GCC compiler is 6.1, processor is x86-64 Intel i5-4690S). So I typed: git clone git@github.com:Ravenbrook/mps.git cd mps/code make -f lii6gc.gmk And the build fails with apss.c: In function ‘stress’: apss.c:82:5: error: dereferencing type-punned pointer might break strict-aliasing rules [-Werror=strict-aliasing] res = make((mps_addr_t *)&ps[i], ap, ss[i]); ^~~ apss.c:125:7: error: dereferencing type-punned pointer might break strict-aliasing rules [-Werror=strict-aliasing] res = make((mps_addr_t *)&ps[i], ap, ss[i]); ^~~ cc1: all warnings being treated as errors comm.gmk:616: recipe for target 'lii6gc/hot/apss.o' failed |
| Analysis | GCC 6.1 is right and the code in apss.c is wrong -- we have a whole section in the manual about this error [2]. "p4 blame" shows that the code in apss.c has been like this since Pekka wrote it in 1999. More seriously, it seems that we are not keeping up to date with GCC releases in our continuous integration. |
| How found | customer |
| Evidence | [1] https://info.ravenbrook.com/mail/2016/08/24/17-36-53/0/[2] http://www.ravenbrook.com/project/mps/.../html/topic/interface.html#type-punning |
| Created by | Gareth Rees |
| Created on | 2016-08-25 09:48:59 |
| Last modified by | Gareth Rees |
| Last modified on | 2018-08-28 11:13:57 |
| History | 2016-08-25 GDR Created. |
| Change | Effect | Date | User | Description |
|---|---|---|---|---|
| 192104 | closed | 2016-09-02 19:20:58 | Gareth Rees | Avoid strict aliasing errors in the MPS test suite, so that it compiles and runs using GCC 6.1. Update the manual entries for mps_alloc and mps_sac_alloc with notes highlighting the problem. |