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Diffstat (limited to 'manual.asciidoc')
| -rw-r--r-- | manual.asciidoc | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/manual.asciidoc b/manual.asciidoc index eefbe12..7aa000e 100644 --- a/manual.asciidoc +++ b/manual.asciidoc @@ -353,9 +353,11 @@ A file is a series of declarations. A declaration can be one of: 2. A build edge, which looks like +build _output1_ _output2_: _rulename_ _input1_ _input2_+. + Implicit dependencies may be tacked on the end with +| - _dependency1_ _dependency2_+. + _dependency1_ _dependency2_+. + Order-only dependencies may be tacked on the end with +|| - _dependency1_ _dependency2_+. + _dependency1_ _dependency2_+. (See <<ref_dependencies,the reference on + dependency types>>.) + 3. Variable declarations, which look like +_variable_ = _value_+. @@ -386,7 +388,7 @@ keys. interpretation by Ninja. `depfile`:: path to an optional `Makefile` that contains extra - _implicit dependencies_ (see the <<ref_dependencies,the reference on + _implicit dependencies_ (see <<ref_dependencies,the reference on dependency types>>). This is explicitly to support `gcc` and its `-M` family of flags, which output the list of headers a given `.c` file depends on. @@ -398,6 +400,11 @@ rule cc depfile = $out.d command = gcc -MMD -MF $out.d [other gcc flags here] ---- ++ +When loading a `depfile`, Ninja implicitly adds edges such that it is +not an error if the listed dependency is missing. This allows you to +delete a depfile-discovered header file and rebuild, without the build +aborting due to a missing input. `description`:: a short description of the command, used to pretty-print @@ -425,14 +432,17 @@ source file of a compile command. 2. _Implicit dependencies_, either as picked up from a `depfile` attribute on a rule or from the syntax +| _dep1_ - _dep2_+ on the end of a build line. Changes in these files cause - the output to be rebuilt; if they are missing, they are just - skipped. + _dep2_+ on the end of a build line. The semantics are identical to + explicit dependencies, the only difference is that implicit dependencies + don't show up in the `$in` variable. + This is for expressing dependencies that don't show up on the command line of the command; for example, for a rule that runs a script, the script itself should be an implicit dependency, as changes to the script should cause the output to rebuild. ++ +Note that dependencies as loaded through depfiles have slightly different +semantics, as described in the <<ref_rule,rule reference>>. 3. _Order-only dependencies_, expressed with the syntax +|| _dep1_ _dep2_+ on the end of a build line. When these are missing, the |