diff options
Diffstat (limited to 'libbuild2/cc/link-rule.hxx')
| -rw-r--r-- | libbuild2/cc/link-rule.hxx | 34 |
1 files changed, 20 insertions, 14 deletions
diff --git a/libbuild2/cc/link-rule.hxx b/libbuild2/cc/link-rule.hxx index 0fc1790..655d36a 100644 --- a/libbuild2/cc/link-rule.hxx +++ b/libbuild2/cc/link-rule.hxx @@ -278,22 +278,28 @@ namespace build2 // have already been executed, then it was for install. // // This has an interesting implication: it means that this rule cannot - // be used to update targets during match. Specifically, we cannot be - // executed for group resolution purposes (not a problem) nor as part - // of the generated source update. The latter case can be a problem: - // imagine a code generator that itself may need to be updated before - // it can be used to re-generate some out-of-date source code. As an - // aside, note that even if we were somehow able to communicate the - // "for install" in this case, the result of such an update may not - // actually be "usable" (e.g., not runnable because of the missing + // be used to update targets to be installed during match (since we + // would notice that they are for install too late). Specifically, we + // cannot be executed for group resolution purposes (should not be a + // problem) nor as part of the generated source update. The latter + // case can be a problem: imagine a source code generator that itself + // may need to be updated before it can be used to re-generate some + // out-of-date source code (or, worse, both the generator and the + // target to be installed depend on the same library). + // + // As an aside, note that even if we were somehow able to communicate + // the "for install" in this case, the result of such an update may + // not actually be "usable" (e.g., not runnable because of the missing // rpaths). There is another prominent case where the result may not - // be usable: cross-compilation. + // be usable: cross-compilation (in fact, if you think about it, "for + // install" is quite similar to cross-compilation: we are building for + // a foreign "environment" and thus cannot execute the results of the + // build). // - // So the current (admittedly fuzzy) thinking is that a project shall - // not try to use its own build for update since it may not be usable - // (because of cross-compilations, being "for install", etc). Instead, - // it should rely on another, "usable" build of itself (this, BTW, is - // related to bpkg's build-time vs run-time dependencies). + // So the current thinking is that a project shall not try to use its + // own "for install" (or, naturally, cross-compilation) build for + // update since it may not be usable. Instead, it should rely on + // another, "usable" build. // optional<bool> for_install; |