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cmd/compile: add sizeCalculationDisabled flag

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Use it to ensure that dowidth is not called
from the backend on a type whose size
has not yet been calculated.

This is an alternative to CL 42016.

Change-Id: I8c7b4410ee4c2a68573102f6b9b635f4fdcf392e
Reviewed-on: https://go-review.googlesource.com/42018
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Josh Bleecher Snyder 2017-04-27 16:37:25 -07:00
parent dae5389d3d
commit c51559813f
4 changed files with 22 additions and 15 deletions
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12
src/cmd/compile/internal/gc/align.go
View file

@ -9,6 +9,10 @@ import (
"sort"
)
// sizeCalculationDisabled indicates whether it is safe
// to calculate Types' widths and alignments. See dowidth.
var sizeCalculationDisabled bool
// machine size and rounding alignment is dictated around
// the size of a pointer, set in betypeinit (see ../amd64/galign.go).
var defercalc int
@ -151,6 +155,10 @@ func widstruct(errtype *types.Type, t *types.Type, o int64, flag int) int64 {
return o
}
// dowidth calculates and stores the size and alignment for t.
// If sizeCalculationDisabled is set, and the size/alignment
// have not already been calculated, it calls Fatal.
// This is used to prevent data races in the back end.
func dowidth(t *types.Type) {
if Widthptr == 0 {
Fatalf("dowidth without betypeinit")
@ -174,6 +182,10 @@ func dowidth(t *types.Type) {
return
}
if sizeCalculationDisabled {
Fatalf("width not calculated: %v", t)
}
// break infinite recursion if the broken recursive type
// is referenced again
if t.Broke() && t.Width == 0 {