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spec: index and array/slice size constants must fit into an int

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R=r, rsc, iant, ken
CC=golang-dev
https://golang.org/cl/6903048
This commit is contained in:
Robert Griesemer 2012-12-12 11:06:26 -08:00
parent 17b3766d18
commit 3906706297
1 changed files with 24 additions and 16 deletions
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40
doc/go_spec.html
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@ -1,6 +1,6 @@
<!--{
"Title": "The Go Programming Language Specification",
"Subtitle": "Version of December 10, 2012",
"Subtitle": "Version of December 12, 2012",
"Path": "/ref/spec"
}-->
@ -815,12 +815,13 @@ ElementType = Type .
</pre>
<p>
The length is part of the array's type and must be a
<a href="#Constant_expressions">constant expression</a> that evaluates to a non-negative
integer value. The length of array <code>a</code> can be discovered
The length is part of the array's type; it must evaluate to a non-
negative <a href="#Constants">constant</a> representable by a value
of type <code>int</code>.
The length of array <code>a</code> can be discovered
using the built-in function <a href="#Length_and_capacity"><code>len</code></a>.
The elements can be addressed by integer <a href="#Index_expressions">indices</a>
indices 0 through <code>len(a)-1</code>.
0 through <code>len(a)-1</code>.
Array types are always one-dimensional but may be composed to form
multi-dimensional types.
</p>
@ -2497,13 +2498,21 @@ The value <code>x</code> is called the
rules apply:
</p>
<p>
If <code>a</code> is not a map:
</p>
<ul>
<li>the index <code>x</code> must be an integer value; it is <i>in range</i> if <code>0 &lt;= x &lt; len(a)</code>,
otherwise it is <i>out of range</i></li>
<li>a <a href="#Constants">constant</a> index must be non-negative
and representable by a value of type <code>int</code>
</ul>
<p>
For <code>a</code> of type <code>A</code> or <code>*A</code>
where <code>A</code> is an <a href="#Array_types">array type</a>:
</p>
<ul>
<li><code>x</code> must be an integer value; it is <i>in range</i> if <code>0 &lt;= x &lt; len(a)</code>,
otherwise it is <i>out of range</i></li>
<li>a <a href="#Constants">constant</a> index must be in range</li>
<li>if <code>a</code> is <code>nil</code> or if <code>x</code> is out of range at run time,
a <a href="#Run_time_panics">run-time panic</a> occurs</li>
@ -2515,9 +2524,6 @@ where <code>A</code> is an <a href="#Array_types">array type</a>:
For <code>a</code> of type <code>S</code> where <code>S</code> is a <a href="#Slice_types">slice type</a>:
</p>
<ul>
<li><code>x</code> must be an integer value; it is <i>in range</i> if <code>0 &lt;= x &lt; len(a)</code>,
otherwise it is <i>out of range</i></li>
<li>a <a href="#Constants">constant</a> index must not be negative</li>
<li>if the slice is <code>nil</code> or if <code>x</code> is out of range at run time,
a <a href="#Run_time_panics">run-time panic</a> occurs</li>
<li><code>a[x]</code> is the slice element at index <code>x</code> and the type of
@ -2529,9 +2535,7 @@ For <code>a</code> of type <code>T</code>
where <code>T</code> is a <a href="#String_types">string type</a>:
</p>
<ul>
<li><code>x</code> must be an integer value; it is <i>in range</i> if <code>0 &lt;= x &lt; len(a)</code>,
otherwise it is <i>out of range</i></li>
<li>a <a href="#Constants">constant</a> index must not be negative, and it must be in range
<li>a <a href="#Constants">constant</a> index must be in range
if the string <code>a</code> is also constant</li>
<li>if <code>x</code> is out of range at run time,
a <a href="#Run_time_panics">run-time panic</a> occurs</li>
@ -2635,7 +2639,9 @@ For arrays or strings, the indices <code>low</code> and <code>high</code> are
<i>in range</i> if <code>0 &lt;= <code>low</code> &lt;= <code>high</code> &lt;= len(a)</code>,
otherwise they are <i>out of range</i>.
For slices, the upper index bound is the slice capacity <code>cap(a)</code> rather than the length.
A <a href="#Constant_expressions">constant</a> index must not be negative, and if both indices
A <a href="#Constants">constant</a> index must be non-negative and representable by a value of type
<code>int</code>.
If both indices
are constant, they must satisfy <code>low &lt;= high</code>. If <code>a</code> is <code>nil</code>
or if the indices are out of range at run time, a <a href="#Run_time_panics">run-time panic</a> occurs.
</p>
@ -4985,8 +4991,9 @@ make(T, n) channel asynchronous channel of type T, buffer size n
<p>
The size arguments <code>n</code> and <code>m</code> must be integer values.
A <a href="#Constants">constant</a> size argument must not be negative, and
if both <code>n</code> and <code>m</code> are provided and are constant, then
A <a href="#Constants">constant</a> size argument must be non-negative and
representable by a value of type <code>int</code>.
If both <code>n</code> and <code>m</code> are provided and are constant, then
<code>n</code> must be no larger than <code>m</code>.
If <code>n</code> is negative or larger than <code>m</code> at run time,
a <a href="#Run_time_panics">run-time panic</a> occurs.
@ -4995,6 +5002,7 @@ a <a href="#Run_time_panics">run-time panic</a> occurs.
<pre>
s := make([]int, 10, 100) // slice with len(s) == 10, cap(s) == 100
s := make([]int, 1e3) // slice with len(s) == cap(s) == 1000
s := make([]int, 1&lt;&lt;63) // illegal: len(s) is not representable by a value of type int
s := make([]int, 10, 0) // illegal: len(s) > cap(s)
c := make(chan int, 10) // channel with a buffer size of 10
m := make(map[string]int, 100) // map with initial space for 100 elements