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Diffstat (limited to 'src/cmd/cgo/doc.go')
| -rw-r--r-- | src/cmd/cgo/doc.go | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/src/cmd/cgo/doc.go b/src/cmd/cgo/doc.go index 605bab6d2..69c7ce893 100644 --- a/src/cmd/cgo/doc.go +++ b/src/cmd/cgo/doc.go @@ -52,6 +52,14 @@ these directives. Package-specific flags should be set using the directives, not the environment variables, so that builds work in unmodified environments. +All the cgo CPPFLAGS and CFLAGS directives in a package are concatenated and +used to compile C files in that package. All the CPPFLAGS and CXXFLAGS +directives in a package are concatenated and used to compile C++ files in that +package. All the LDFLAGS directives in any package in the program are +concatenated and used at link time. All the pkg-config directives are +concatenated and sent to pkg-config simultaneously to add to each appropriate +set of command-line flags. + When the Go tool sees that one or more Go files use the special import "C", it will look for other non-Go files in the directory and compile them as part of the Go package. Any .c, .s, or .S files will be @@ -63,11 +71,26 @@ compilers may be changed by the CC and CXX environment variables, respectively; those environment variables may include command line options. +To enable cgo during cross compiling builds, set the CGO_ENABLED +environment variable to 1 when building the Go tools with make.bash. +Also, set CC_FOR_TARGET to the C cross compiler for the target. CC will +be used for compiling for the host. + +After the Go tools are built, when running the go command, CC_FOR_TARGET is +ignored. The value of CC_FOR_TARGET when running make.bash is the default +compiler. However, you can set the environment variable CC, not CC_FOR_TARGET, +to control the compiler when running the go tool. + +CXX_FOR_TARGET works in a similar way for C++ code. + Go references to C Within the Go file, C's struct field names that are keywords in Go can be accessed by prefixing them with an underscore: if x points at a C struct with a field named "type", x._type accesses the field. +C struct fields that cannot be expressed in Go, such as bit fields +or misaligned data, are omitted in the Go struct, replaced by +appropriate padding to reach the next field or the end of the struct. The standard C numeric types are available under the names C.char, C.schar (signed char), C.uchar (unsigned char), @@ -84,6 +107,11 @@ C's union types are represented as a Go byte array with the same length. Go structs cannot embed fields with C types. +Cgo translates C types into equivalent unexported Go types. +Because the translations are unexported, a Go package should not +expose C types in its exported API: a C type used in one Go package +is different from the same C type used in another. + Any C function (even void functions) may be called in a multiple assignment context to retrieve both the return value (if any) and the C errno variable as an error (use _ to skip the result value if the |