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document initialization

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OCL=13369
CL=13369
This commit is contained in:
Rob Pike 2008-07-22 17:53:53 -07:00
parent 35b7a174e6
commit f4dcf51846
1 changed files with 33 additions and 3 deletions
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36
doc/go_lang.txt
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@ -50,10 +50,9 @@ By convention, one package, by default called main, is the starting point for
execution. It contains a function, also called main, that is the first function
invoked by the run time system.
If any package within the program
If a source file within the program
contains a function init(), that function will be executed
before main.main() is called. The details of initialization are
still under development.
before main.main() is called.
Source files can be compiled separately (without the source
code of packages they depend on), but not independently (the compiler does
@ -2110,9 +2109,40 @@ followed by a series of declarations.
Program = PackageClause { ImportDecl [ ";" ] } { Declaration [ ";" ] } .
Initialization and Program Execution
----
A package with no imports is initialized by assigning initial values to
all its global variables in declaration order and then calling any init()
functions defined in its source. Since a package may contain more
than one source file, there may be more than one init() function, but
only one per source file.
If a package has imports, the imported packages are initialized
before initializing the package itself. If multiple packages import
a package P, P will be initialized only once.
The importing of packages, by construction, guarantees that there can
be no cyclic dependencies in initialization.
A complete program, possibly created by linking multiple packages,
must have one package called main, with a function
func main() { ... }
defined. The function main.main() takes no arguments and returns no
value.
Program execution begins by initializing the main package and then
invoking main.main().
When main.main() returns, the program exits.
TODO: is there a way to override the default for package main or the
default for the function name main.main?
TODO
----
- TODO: type switch?
- TODO: words about slices
- TODO: really lock down semicolons
- TODO: need to talk (perhaps elsewhere) about libraries, sys.exit(), etc.