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go/misc/cgo/testshared/testdata
Cherry Zhang 7799756a50 cmd/link: fix GC data reading from shared library (attempt 2)
When linking against a Go shared library, when a global variable
in the main module has a type defined in the shared library, the
linker needs to pull the GC data from the shared library to build
the GC program for the global variable. Currently, this fails
silently, as the shared library file is closed too early and the
read failed (with no error check), causing a zero GC map emitted
for the variable, which in turn causes the runtime to treat the
variable as pointerless.

For now, fix this by keeping the file open. In the future we may
want to use mmap to read from the shared library instead.

Also add error checking. And fix a (mostly harmless) mistake in
size caluculation.

Also remove an erroneous condition for ARM64. ARM64 used to have
a special case to get the addend from the relocation on the
gcdata field. That was removed, but the new code accidentally
returned 0 unconditionally. It's no longer necessary to have any
special case, since the addend is now applied directly to the
gcdata field on ARM64, like on all the other platforms.

Fixes #39927.

This is the second attempt of CL 240462. And this reverts
CL 240616.

Change-Id: I01c82422b9f67e872d833336885935bc509bc91b
Reviewed-on: https://go-review.googlesource.com/c/go/+/240621
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
2020-07-01 14:41:56 +00:00
..
dep2
dep3
depBase
division
exe
exe2
exe3
execgo
explicit
gcdata cmd/link: fix GC data reading from shared library (attempt 2) 2020-07-01 14:41:56 +00:00
global
globallib
iface
iface_a
iface_b
iface_i
implicit
implicitcmd
issue25065
issue30768
issue39777 cmd/link: skip zero values in fingerprint check 2020-06-23 18:38:32 +00:00
trivial