diff options
Diffstat (limited to 'libbuild2/cxx/init.cxx')
| -rw-r--r-- | libbuild2/cxx/init.cxx | 80 |
1 files changed, 56 insertions, 24 deletions
diff --git a/libbuild2/cxx/init.cxx b/libbuild2/cxx/init.cxx index 6a449c7..d4e3151 100644 --- a/libbuild2/cxx/init.cxx +++ b/libbuild2/cxx/init.cxx @@ -58,7 +58,36 @@ namespace build2 uint64_t mi (ci.version.minor); uint64_t p (ci.version.patch); - // Features. + // Besides various `c++NN` we have two special values: `latest` and + // `experimental`. + // + // The semantics of the `latest` value is the latest available standard + // that is not necessarily complete or final but is practically usable. + // In other words, a project that uses this value and does not rely on + // any unstable/bleeding edge parts of the standard (or takes care to + // deal with them, for example, using feature test macros), can + // reasonably expect to work. In particular, this is the value we use by + // default in projects created by bdep-new(1) as well as to build the + // build2 toolchain itself. + // + // The `experimental` value, as the name suggests, is the latest + // available standard that is not necessarily usable in real projects. + // By definition, `experimental` >= `latest`. + // + // In addition to the `experimental` value itself we have a number of + // feature flags that can be used to enable or disable certain major + // parts (such as modules, concepts, etc) in this mode. They are also + // used to signal back to the project whether a particular feature is + // available. A feature flag set by the user has a tri-state semantics: + // + // - false - disabled + // - unspecified - enabled if practically usable + // - true - enabled even if practically unusable + // + bool latest (v != nullptr && *v == "latest"); + bool experimental (v != nullptr && *v == "experimental"); + + // Feature flags. // auto enter = [&rs] (const char* v) -> const variable& { @@ -66,19 +95,11 @@ namespace build2 v, variable_visibility::project); }; - // NOTE: see also module sidebuild subproject if changing anything about - // modules here. - //bool concepts (false); auto& v_c (enter ("cxx.features.concepts")); bool modules (false); auto& v_m (enter ("cxx.features.modules")); - // Translate "latest" and "experimental" to the compiler/version- - // appropriate option(s). Experimental is normally like latest with - // extra stuff enabled via additional flags. Otherwise translate the - // standard value. - // - bool experimental ( v != nullptr && *v == "experimental"); - bool latest (experimental || (v != nullptr && *v == "latest")); + // NOTE: see also module sidebuild subproject if changing anything about + // modules here. string o; @@ -91,6 +112,10 @@ namespace build2 // to c++14 but can be set to c++latest. And from 15.3 it can be // c++17. // + bool v16_0 ( mj > 19 || (mj == 19 && mi >= 20)); + bool v15_3 (v16_0 || (mj == 19 && mi >= 11)); + bool v14_3 (v15_3 || (mj == 19 && (mi > 0 || (mi == 0 && p >= 24215)))); + // The question is also whether we should verify that the requested // standard is provided by this VC version. And if so, from which // version should we say VC supports 11, 14, and 17? We should @@ -100,9 +125,21 @@ namespace build2 // // For now we are not going to bother doing this for C++03. // - if (latest) + if (experimental) { - if (mj > 19 || (mj == 19 && (mi > 0 || (mi == 0 && p >= 24215)))) + if (v14_3) + o = "/std:c++latest"; + } + else if (latest) + { + // We used to map `latest` to `c++latest` but starting from 16.1, + // VC seem to have adopted the "move fast and break things" motto + // for this mode. So starting from 16 we only enable it in + // `experimental`. + // + if (v16_0) + o = "/std:c++17"; + else if (v14_3) o = "/std:c++latest"; } else if (v == nullptr) @@ -131,12 +168,12 @@ namespace build2 fail << "C++" << *v << " is not supported by " << ci.signature << info << "required by " << project (rs) << '@' << rs; - if (mj > 19 || (mj == 19 && mi >= 11)) // 15.3 + if (v15_3) { if (*v == "14") o = "/std:c++14"; else if (*v == "17") o = "/std:c++17"; } - else if (mj == 19 && (mi > 0 || (mi == 0 && p >= 24215))) // 14.3 + else if (v14_3) { if (*v == "14") o = "/std:c++14"; else if (*v == "17") o = "/std:c++latest"; @@ -150,7 +187,7 @@ namespace build2 } case compiler_class::gcc: { - if (latest) + if (latest || experimental) { switch (ct) { @@ -247,8 +284,8 @@ namespace build2 { // Starting with 15.5 (19.12) Visual Studio-created projects // default to the strict mode. However, this flag currently tends - // to trigger too many compiler bugs. So for now we leave it - // to the experimenters to enjoy. + // to trigger too many compiler bugs. So for now we leave it to + // the experimenters to enjoy. // if (mj > 19 || (mj == 19 && mi >= 12)) r.push_back ("/permissive-"); @@ -259,12 +296,7 @@ namespace build2 break; } - // Unless disabled by the user, try to enable C++ modules. Here we use - // a tri-state: - // - // - false - disabled - // - unspecified - enabled if practically usable - // - true - enabled even if practically unusable + // Unless disabled by the user, try to enable C++ modules. // lookup l; if (!(l = rs[v_m]) || cast<bool> (l)) |