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Diffstat (limited to 'build2/context.hxx')
| -rw-r--r-- | build2/context.hxx | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/build2/context.hxx b/build2/context.hxx index 9c43da1..cfe770f 100644 --- a/build2/context.hxx +++ b/build2/context.hxx @@ -289,6 +289,31 @@ namespace build2 // extern const variable* var_backlink; // [string] target visibility + // Prerequisite inclusion/exclusion. Valid values are: + // + // false - exclude. + // true - include. + // adhoc - include but treat as an ad hoc input. + // + // If a rule uses prerequisites as inputs (as opposed to just matching them + // with the "pass-through" semantics), then the adhoc value signals that a + // prerequisite is an ad hoc input. A rule should match and execute such a + // prerequisite (whether its target type is recognized as suitable input or + // not) and assume that the rest will be handled by the user (e.g., it will + // be passed via a command line argument or some such). Note that this + // mechanism can be used to both treat unknown prerequisite types as inputs + // (for example, linker scripts) as well as prevent treatment of known + // prerequisite types as such while still matching and executing them (for + // example, plugin libraries). + // + // A rule with the "pass-through" semantics should treat the adhoc value + // the same as true. + // + // To query this value in rule implementations use the include() helpers + // from prerequisites.hxx. + // + extern const variable* var_include; // [string] prereq visibility + extern const char var_extension[10]; // "extension" // The build.* namespace. |