Documentation
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Overview ¶
Package build gathers information about Go packages.
Go Path ¶
The Go path is a list of directory trees containing Go source code. It is consulted to resolve imports that cannot be found in the standard Go tree. The default path is the value of the GOPATH environment variable, interpreted as a path list appropriate to the operating system (on Unix, the variable is a colon-separated string; on Windows, a semicolon-separated string; on Plan 9, a list).
Each directory listed in the Go path must have a prescribed structure:
The src/ directory holds source code. The path below 'src' determines the import path or executable name.
The pkg/ directory holds installed package objects. As in the Go tree, each target operating system and architecture pair has its own subdirectory of pkg (pkg/GOOS_GOARCH).
If DIR is a directory listed in the Go path, a package with source in DIR/src/foo/bar can be imported as "foo/bar" and has its compiled form installed to "DIR/pkg/GOOS_GOARCH/foo/bar.a" (or, for gccgo, "DIR/pkg/gccgo/foo/libbar.a").
The bin/ directory holds compiled commands. Each command is named for its source directory, but only using the final element, not the entire path. That is, the command with source in DIR/src/foo/quux is installed into DIR/bin/quux, not DIR/bin/foo/quux. The foo/ is stripped so that you can add DIR/bin to your PATH to get at the installed commands.
Here's an example directory layout:
GOPATH=/home/user/gocode
/home/user/gocode/
src/
foo/
bar/ (go code in package bar)
x.go
quux/ (go code in package main)
y.go
bin/
quux (installed command)
pkg/
linux_amd64/
foo/
bar.a (installed package object)
Build Constraints ¶
A build constraint is a line comment beginning with the directive +build that lists the conditions under which a file should be included in the package. Constraints may appear in any kind of source file (not just Go), but they must appear near the top of the file, preceded only by blank lines and other line comments.
A build constraint is evaluated as the OR of space-separated options; each option evaluates as the AND of its comma-separated terms; and each term is an alphanumeric word or, preceded by !, its negation. That is, the build constraint:
// +build linux,386 darwin,!cgo
corresponds to the boolean formula:
(linux AND 386) OR (darwin AND (NOT cgo))
A file may have multiple build constraints. The overall constraint is the AND of the individual constraints. That is, the build constraints:
// +build linux darwin // +build 386
corresponds to the boolean formula:
(linux OR darwin) AND 386
During a particular build, the following words are satisfied:
- the target operating system, as spelled by runtime.GOOS
- the target architecture, as spelled by runtime.GOARCH
- the compiler being used, currently either "gc" or "gccgo"
- "cgo", if ctxt.CgoEnabled is true
- any additional words listed in ctxt.BuildTags
If a file's name, after stripping the extension and a possible _test suffix, matches *_GOOS, *_GOARCH, or *_GOOS_GOARCH for any known operating system and architecture values, then the file is considered to have an implicit build constraint requiring those terms.
To keep a file from being considered for the build:
// +build ignore
(any other unsatisfied word will work as well, but “ignore” is conventional.)
To build a file only when using cgo, and only on Linux and OS X:
// +build linux,cgo darwin,cgo
Such a file is usually paired with another file implementing the default functionality for other systems, which in this case would carry the constraint:
// +build !linux,!darwin !cgo
Naming a file dns_windows.go will cause it to be included only when building the package for Windows; similarly, math_386.s will be included only when building the package for 32-bit x86.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ToolDir = filepath.Join(runtime.GOROOT(), "pkg/tool/"+runtime.GOOS+"_"+runtime.GOARCH)
ToolDir is the directory containing build tools.
Functions ¶
func ArchChar ¶
ArchChar returns the architecture character for the given goarch. For example, ArchChar("amd64") returns "6".
func IsLocalImport ¶
IsLocalImport reports whether the import path is a local import path, like ".", "..", "./foo", or "../foo".
Types ¶
type Context ¶
type Context struct {
GOARCH string // target architecture
GOOS string // target operating system
GOROOT string // Go root
GOPATH string // Go path
CgoEnabled bool // whether cgo can be used
BuildTags []string // additional tags to recognize in +build lines
InstallTag string // package install directory suffix
UseAllFiles bool // use files regardless of +build lines, file names
Compiler string // compiler to assume when computing target paths
// JoinPath joins the sequence of path fragments into a single path.
// If JoinPath is nil, Import uses filepath.Join.
JoinPath func(elem ...string) string
// SplitPathList splits the path list into a slice of individual paths.
// If SplitPathList is nil, Import uses filepath.SplitList.
SplitPathList func(list string) []string
// IsAbsPath reports whether path is an absolute path.
// If IsAbsPath is nil, Import uses filepath.IsAbs.
IsAbsPath func(path string) bool
// IsDir reports whether the path names a directory.
// If IsDir is nil, Import calls os.Stat and uses the result's IsDir method.
IsDir func(path string) bool
// HasSubdir reports whether dir is a subdirectory of
// (perhaps multiple levels below) root.
// If so, HasSubdir sets rel to a slash-separated path that
// can be joined to root to produce a path equivalent to dir.
// If HasSubdir is nil, Import uses an implementation built on
// filepath.EvalSymlinks.
HasSubdir func(root, dir string) (rel string, ok bool)
// ReadDir returns a slice of os.FileInfo, sorted by Name,
// describing the content of the named directory.
// If ReadDir is nil, Import uses ioutil.ReadDir.
ReadDir func(dir string) (fi []os.FileInfo, err error)
// OpenFile opens a file (not a directory) for reading.
// If OpenFile is nil, Import uses os.Open.
OpenFile func(path string) (r io.ReadCloser, err error)
}
A Context specifies the supporting context for a build.
var Default Context = defaultContext()
Default is the default Context for builds. It uses the GOARCH, GOOS, GOROOT, and GOPATH environment variables if set, or else the compiled code's GOARCH, GOOS, and GOROOT.
func (*Context) Import ¶
Import returns details about the Go package named by the import path, interpreting local import paths relative to the srcDir directory. If the path is a local import path naming a package that can be imported using a standard import path, the returned package will set p.ImportPath to that path.
In the directory containing the package, .go, .c, .h, and .s files are considered part of the package except for:
- .go files in package documentation
- files starting with _ or . (likely editor temporary files)
- files with build constraints not satisfied by the context
If an error occurs, Import returns a non-nil error and a non-nil *Package containing partial information.
type ImportMode ¶
type ImportMode uint
An ImportMode controls the behavior of the Import method.
const ( // If FindOnly is set, Import stops after locating the directory // that should contain the sources for a package. It does not // read any files in the directory. FindOnly ImportMode = 1 << iota // If AllowBinary is set, Import can be satisfied by a compiled // package object without corresponding sources. AllowBinary )
type NoGoError ¶
type NoGoError struct {
Dir string
}
NoGoError is the error used by Import to describe a directory containing no Go source files.
type Package ¶
type Package struct {
Dir string // directory containing package sources
Name string // package name
Doc string // documentation synopsis
ImportPath string // import path of package ("" if unknown)
Root string // root of Go tree where this package lives
SrcRoot string // package source root directory ("" if unknown)
PkgRoot string // package install root directory ("" if unknown)
BinDir string // command install directory ("" if unknown)
Goroot bool // package found in Go root
PkgObj string // installed .a file
// Source files
GoFiles []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
CgoFiles []string // .go source files that import "C"
CFiles []string // .c source files
HFiles []string // .h source files
SFiles []string // .s source files
SysoFiles []string // .syso system object files to add to archive
SwigFiles []string // .swig files
SwigCXXFiles []string // .swigcxx files
// Cgo directives
CgoPkgConfig []string // Cgo pkg-config directives
CgoCFLAGS []string // Cgo CFLAGS directives
CgoLDFLAGS []string // Cgo LDFLAGS directives
// Dependency information
Imports []string // imports from GoFiles, CgoFiles
ImportPos map[string][]token.Position // line information for Imports
// Test information
TestGoFiles []string // _test.go files in package
TestImports []string // imports from TestGoFiles
TestImportPos map[string][]token.Position // line information for TestImports
XTestGoFiles []string // _test.go files outside package
XTestImports []string // imports from XTestGoFiles
XTestImportPos map[string][]token.Position // line information for XTestImports
}
A Package describes the Go package found in a directory.
func Import ¶
func Import(path, srcDir string, mode ImportMode) (*Package, error)
Import is shorthand for Default.Import.
Source Files