cmd/gc: int should be 64 bits wide on 64-bit platforms #2188
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Comment 4 by jp@webmaster.ms: I did not mean to make int longer. Somebody changed the subject line. I talked about arrays only. Currently, make() and [] accept ANY integral type without explicit conversion to int: a := make([]int32, byte(2)) println(a[byte(1)]) Can they deal appropriately with integrals longer than int (uint32,int64,uint64) ? a := make([]int8, uint64(1<<32+2)) println(a[uint64(1<<32)]) |
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Comment 6 by webmaster@webmaster.ms: len() can have a "fuzzy" integral type, similar to parameter of make() In "len(a) + int(1)" it is int. In "len(a) < byte(1)" it is byte. In "println(len(a))" or "x := len(a)" it is uintptr. It is also similar to the type of numeric constant (they can be used as any integral type without explicit conversion) but with defaulting to uintptr instead of int. |
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Comment 7 by webmaster@webmaster.ms: I understand from the maillist, you insist on len() to be int only to have ability to write "for i:=0; i<len(x); i++". This will be possible. As well as "for i:=uint64(0); i<len(x); i++" for long arrays. |
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Comment 8 by webmaster@webmaster.ms: I understand from the maillist, you insist on len() to be int only to have ability to write "for i:=0; i<len(x); i++". This will be possible. As well as "for i:=uint64(0); i<len(x); i++" for long arrays. But this will fail (size is uintptr, i is int: size:=len(x) for i:=0; i<size; i++ |
Discussing language changes in the issue tracker
is not particularly productive. If you'd like to continue
this conversation please reply to that thread in
golang-nuts. But please also read it first.
The problem with a fuzzy len is that if you write
for i := 0; i < len(x); i++ {
and i has type int but len(x) is some fuzzy number
that is bigger than any possible int, then the loop
will be wrong: it will wrap around and die using i
as a (negative) loop index.
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There have been lots of recent relevant commits. hg log -k 'Update issue #2188' :-( |
What is the use of "update issue #2188" if they don't show up here? |
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This issue was closed by revision 10ea651. Status changed to Fixed. |
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by webmaster@webmaster.ms:
Number of arrays items are limited to 2^31 even on 64 bit platforms testcase: ============================ package main func main() { a := make([]int32, 2*1000*1000*1000) // 8Gb alloc, ok println(len(a)) b := make([]int8, 3*1000*1000*1000) // 3Gb alloc, failed println(len(b)) } ============================The text was updated successfully, but these errors were encountered: