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spec: document new program initialization process 

For #57411.

Change-Id: I94982d939d16ad17174f801cc167cc10ddc8da30
Reviewed-on: https://go-review.googlesource.com/c/go/+/501696
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Bypass: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Robert Griesemer 2023-06-07 16:56:28 -07:00
parent 886fba5871
commit ee5af6103d
1 changed files with 25 additions and 14 deletions
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39
doc/go_spec.html
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@ -1,6 +1,6 @@
<!--{
"Title": "The Go Programming Language Specification",
"Subtitle": "Version of June 7, 2023",
"Subtitle": "Version of June 13, 2023",
"Path": "/ref/spec"
}-->
@ -8003,6 +8003,9 @@ The declaration order of variables declared in multiple files is determined
by the order in which the files are presented to the compiler: Variables
declared in the first file are declared before any of the variables declared
in the second file, and so on.
To ensure reproducible initialization behavior, build systems are encouraged
to present multiple files belonging to the same package in lexical file name
order to a compiler.
</p>
<p>
@ -8113,15 +8116,30 @@ in a program.
</p>
<p>
A package with no imports is initialized by assigning initial values
to all its package-level variables followed by calling all <code>init</code>
functions in the order they appear in the source, possibly in multiple files,
as presented to the compiler.
The entire package is initialized by assigning initial values
to all its package-level variables followed by calling
all <code>init</code> functions in the order they appear
in the source, possibly in multiple files, as presented
to the compiler.
</p>
<h3 id="Program_initialization">Program initialization</h3>
<p>
The packages of a complete program are initialized stepwise, one package at a time.
If a package has imports, the imported packages are initialized
before initializing the package itself. If multiple packages import
a package, the imported package will be initialized only once.
The importing of packages, by construction, guarantees that there
can be no cyclic initialization dependencies.
More precisely:
</p>
<p>
Given the list of all packages, sorted by import path, in each step the first
uninitialized package in the list for which all imported packages (if any) are
already initialized is <a href="#Package_initialization">initialized</a>.
This step is repeated until all packages are initialized.
</p>
<p>
@ -8135,13 +8153,6 @@ the <code>init</code> functions: it will not invoke the next one
until the previous one has returned.
</p>
<p>
To ensure reproducible initialization behavior, build systems are encouraged
to present multiple files belonging to the same package in lexical file name
order to a compiler.
</p>
<h3 id="Program_execution">Program execution</h3>
<p>
A complete program is created by linking a single, unimported package
@ -8157,8 +8168,8 @@ func main() { … }
</pre>
<p>
Program execution begins by initializing the main package and then
invoking the function <code>main</code>.
Program execution begins by <a href="#Program_initialization">initializing the program</a>
and then invoking the function <code>main</code> in package <code>main</code>.
When that function invocation returns, the program exits.
It does not wait for other (non-<code>main</code>) goroutines to complete.
</p>