| Title | MPS buildsys CONFIG_PF_* does not select a platform, is not checked by mpstd.h |
| Status | closed |
| Priority | essential |
| Assigned user | Richard Kistruck |
| Organization | Ravenbrook |
| Description | MPS buildsys CONFIG_PF_* does not select a platform, is not checked by mpstd.h Related jobs: job001944 "MPS lacks separate w3i3m9 platform for building with VC9 (Microsoft Visual C++ 9.0)" (desires checking) RHSK 2008-10-22 See notes in mpstd.h: //info.ravenbrook.com/project/mps/branch/2008-08-14/vc9/code/mpstd.h#3MPS buildsystems know the platform. Also, file "mpstd.h" detects the platform. The CONFIG_PF_* preprocessor symbol is intended to be used by the buildsystem to control / override / augment the detection in mpstd.h. It fails to do so, because if mpstd.h detects the characteristic preprocessor symbols set by a particular compiler that happens to occur earlier in mpstd.h's list of platforms, this will take effect, and the CONFIG_PF_* that is attempting to select a later platfrom will be ignored. It would be much more useful for mpstd.h to always determine the platform (by looking for the characteristic preprocessor symbols), and then check that the answer reached matches the CONFIG_PF_* specified by the buildsys (if the buildsys does specify it; not all do). But mpstd.h does not do this. |
| Analysis | RHSK 2008-10-22 CONFIG_PF_* does not reliably select a platform, as described above. C preprocessor is limited: no string comparisons or wildcards. While it would be possible allow CONFIG_PF_* to override, this would require running through every possible platform twice, once for CONFIG_PF_* and then looking for the characteristic preprocessor symbols. It's not worth it. There's no need to override. mpstd.h *has* to work without buildsystem support anyway, when included by client code. However, a check would be very useful, and CONFIG_PF_* can be used for this: this is how the buildsys tells mpstd.h what platform it is trying to build. Because there is no wildcard matching, the easiest way for the buildsys to tell mpstd.h that it has set a particular CONFIG_PF_* is for it to also set another symbol. I have chosen CONFIG_PF_STRING. The string value is not currently used; the presence of CONFIG_PF_STRING is merely a flag. Now, for platforms that set BOTH CONFIG_PF_* and CONFIG_PF_STRING, mpstd.h halts if there is a mismatch with the platform it determines. This enables checking that the right version of the compiler is in use: see job001944. |
| How found | unknown |
| Evidence | none |
| Observed in | 1.108.2 |
| Created by | Richard Kistruck |
| Created on | 2008-10-22 17:53:16 |
| Last modified by | Richard Kistruck |
| Last modified on | 2008-10-22 18:00:38 |
| History | 2008-10-22 RHSK Created. |
| Change | Effect | Date | User | Description |
|---|---|---|---|---|
| 166513 | closed | 2008-10-21 18:32:26 | Richard Kistruck | MPS br/vc9: mpstd.h: (for all remaining platforms) - fix broken behaviour if CONFIG_PF_* is set (result depends on order of the various platform elifs!); change it to always use platform detection by looking at preprocessor symbols, and then (if CONFIG_PF_STRING *and* CONFIG_PF_* are set) check that CONFIG and detection match; xcppgc.gmk: define both CONFIG_PF_STRING and CONFIG_PF_*. |
| 166512 | open | 2008-10-21 17:44:17 | Richard Kistruck | MPS br/vc9: mpstd.h: - fix broken behaviour if CONFIG_PF_* is set (result depends on order of the various platform elifs!); change it to always use platform detection by looking at preprocessor symbols, and then (if CONFIG_PF_STRING *and* CONFIG_PF_* are set) check that CONFIG and detection match; - write design notes about interaction of CONFIG_PF_* and platform detection. w3i3m[v9].nmk: define both CONFIG_PF_STRING and CONFIG_PF_*. |