On Saturday, November 13, 2021 at 12:48:41 PM UTC-6 seank...@gmail.com
wrote:
> global variables are stored in there data section of the compiled binary,
> the linker imposes a 2GB size limit
> the array in main can be allocated at runtime, and given enough memory, it
> could succeed
>
>
Why does the linker impose a 2GB limit on .bss data but not heap memory? Is
there a limit on heap variables?
>
> On Saturday, November 13, 2021 at 5:46:29 PM UTC arthurwil...@gmail.com
> wrote:
>
>> On a 64bit Mac, this code:
>>
>> package main
>>
>> var X [^uint(0)>>14]byte
>> func main() {
>> }
>>
>> produces a compile time error:
>> main.X: symbol too large (1125899906842623 bytes > 2000000000 bytes)
>>
>> But this compiles and crashes at runtime.
>>
>> package main
>>
>> func main() {
>> var X [^uint(0) >> 14]byte
>> _ = X
>> }
>>
>> runtime: out of memory: cannot allocate 1125899906842624-byte block
>> (3997696 in use)
>> fatal error: out of memory
>>
>> goroutine 1 [running]:
>> runtime.throw({0x1061335, 0x11})
>> /usr/local/go/src/runtime/panic.go:1198 +0x71 fp=0xc000042658
>> sp=0xc000042628 pc=0x102b031
>> runtime.(*mcache).allocLarge(0x100a734, 0x3ffffffffffff, 0x11, 0x1)
>> /usr/local/go/src/runtime/mcache.go:229 +0x22e fp=0xc0000426b8
>> sp=0xc000042658 pc=0x101086e
>> runtime.mallocgc(0x3ffffffffffff, 0x1059300, 0x1)
>> /usr/local/go/src/runtime/malloc.go:1082 +0x5c5 fp=0xc000042738
>> sp=0xc0000426b8 pc=0x100a645
>> runtime.newobject(0x1058a00)
>> /usr/local/go/src/runtime/malloc.go:1228 +0x27 fp=0xc000042760
>> sp=0xc000042738 pc=0x100aa87
>> main.main()
>> /Users/billmorgan/git/tmp/main.go:5 +0x25 fp=0xc000042780
>> sp=0xc000042760 pc=0x1054c65
>> runtime.main()
>> /usr/local/go/src/runtime/proc.go:255 +0x227 fp=0xc0000427e0
>> sp=0xc000042780 pc=0x102d6c7
>> runtime.goexit()
>> /usr/local/go/src/runtime/asm_amd64.s:1581 +0x1 fp=0xc0000427e8
>> sp=0xc0000427e0 pc=0x1051fa1
>>
>>
>> Why does the 2nd program succeed compilation of the same array that
>> failed compilation in the 1st program?
>>
>> It was known ahead of time that the allocation would fail so I think the
>> 2nd program should have failed to compile too.
>>
>>
>>
>>
>>
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