cmd/compile, cmd/link: weak relocation for ptrTo

Introduce R_WEAKADDROFF, a "weak" variation of the R_ADDROFF relocation
that will only reference the type described if it is in some other way
reachable.

Use this for the ptrToThis field in reflect type information where it
is safe to do so (that is, types that don't need to be included for
interface satisfaction, and types that won't cause the compiler to
recursively generate an endless series of ptr-to-ptr-to-ptr-to...
types).

Also fix a small bug in reflect, where StructOf was not clearing the
ptrToThis field of new types.

Fixes #17931

Change-Id: I4d3b53cb9c916c97b3b16e367794eee142247281
Reviewed-on: https://go-review.googlesource.com/33427
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
David Crawshaw 2016-11-21 16:58:55 -05:00
parent aeaa4c3c1d
commit 6f31abd23a
8 changed files with 54 additions and 5 deletions

View file

@ -538,6 +538,11 @@ const (
// R_ADDROFF resolves to a 32-bit offset from the beginning of the section
// holding the data being relocated to the referenced symbol.
R_ADDROFF
// R_WEAKADDROFF resolves just like R_ADDROFF but is a weak relocation.
// A weak relocation does not make the symbol it refers to reachable,
// and is only honored by the linker if the symbol is in some other way
// reachable.
R_WEAKADDROFF
R_SIZE
R_CALL
R_CALLARM