Backport fix allowing LTO to be enabled on cgo sources
Resolves: rhbz#1904567
This commit is contained in:
Derek Parker
parent
677ea6b2c5
commit
c244cf46b0
289
cgo-lto-fix.patch
Normal file
289
cgo-lto-fix.patch
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@ -0,0 +1,289 @@
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From 24e9707cbfa6b1ed6abdd4b11f9ddaf3aac5ad88 Mon Sep 17 00:00:00 2001
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From: Ian Lance Taylor <iant@golang.org>
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Date: Tue, 25 May 2021 16:31:41 -0700
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Subject: [PATCH] cmd/link, cmd/cgo: support -flto in CFLAGS
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The linker now accepts unrecognized object files in external linking mode.
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These objects will simply be passed to the external linker.
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This permits using -flto which can generate pure byte code objects,
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whose symbol table the linker does not know how to read.
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The cgo tool now passes -fno-lto when generating objects whose symbols
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it needs to read. The cgo tool now emits matching types in different
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objects, so that the lto linker does not report a mismatch.
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This is based on https://golang.org/cl/293290 by Derek Parker.
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For #43505
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Fixes #43830
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Fixes #46295
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Change-Id: I6787de213417466784ddef5af8899e453b4ae1ad
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Reviewed-on: https://go-review.googlesource.com/c/go/+/322614
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Trust: Ian Lance Taylor <iant@golang.org>
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Run-TryBot: Ian Lance Taylor <iant@golang.org>
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TryBot-Result: Go Bot <gobot@golang.org>
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Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
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---
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diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
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index ae61725..a73e998 100644
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--- a/src/cmd/cgo/gcc.go
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+++ b/src/cmd/cgo/gcc.go
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@@ -1638,6 +1638,8 @@
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c = append(c, "-maix64")
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c = append(c, "-mcmodel=large")
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}
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+ // disable LTO so we get an object whose symbols we can read
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+ c = append(c, "-fno-lto")
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c = append(c, "-") //read input from standard input
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return c
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}
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diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
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index 8c31d5b..94152f4 100644
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--- a/src/cmd/cgo/out.go
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+++ b/src/cmd/cgo/out.go
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@@ -168,8 +168,18 @@
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if *gccgo {
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fmt.Fprintf(fc, "extern byte *%s;\n", n.C)
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} else {
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- fmt.Fprintf(fm, "extern char %s[];\n", n.C)
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- fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C)
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+ // Force a reference to all symbols so that
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+ // the external linker will add DT_NEEDED
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+ // entries as needed on ELF systems.
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+ // Treat function variables differently
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+ // to avoid type confict errors from LTO
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+ // (Link Time Optimization).
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+ if n.Kind == "fpvar" {
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+ fmt.Fprintf(fm, "extern void %s();\n", n.C)
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+ } else {
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+ fmt.Fprintf(fm, "extern char %s[];\n", n.C)
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+ fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C)
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+ }
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fmt.Fprintf(fgo2, "//go:linkname __cgo_%s %s\n", n.C, n.C)
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fmt.Fprintf(fgo2, "//go:cgo_import_static %s\n", n.C)
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fmt.Fprintf(fgo2, "var __cgo_%s byte\n", n.C)
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@@ -1042,7 +1052,7 @@
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fmt.Fprintf(fgo2, "//go:cgo_export_static _cgoexp%s_%s\n", cPrefix, exp.ExpName)
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fmt.Fprintf(fgo2, "func _cgoexp%s_%s(a *%s) {\n", cPrefix, exp.ExpName, gotype)
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- fmt.Fprintf(fm, "int _cgoexp%s_%s;\n", cPrefix, exp.ExpName)
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+ fmt.Fprintf(fm, "void _cgoexp%s_%s(void* p){}\n", cPrefix, exp.ExpName)
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if gccResult != "void" {
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// Write results back to frame.
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diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
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index 50bf80b..bc49c6d 100644
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--- a/src/cmd/dist/test.go
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+++ b/src/cmd/dist/test.go
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@@ -722,14 +722,29 @@
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},
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})
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if t.hasCxx() {
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- t.tests = append(t.tests, distTest{
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- name: "swig_callback",
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- heading: "../misc/swig/callback",
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- fn: func(dt *distTest) error {
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- t.addCmd(dt, "misc/swig/callback", t.goTest())
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- return nil
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+ t.tests = append(t.tests,
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+ distTest{
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+ name: "swig_callback",
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+ heading: "../misc/swig/callback",
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+ fn: func(dt *distTest) error {
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+ t.addCmd(dt, "misc/swig/callback", t.goTest())
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+ return nil
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+ },
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},
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- })
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+ distTest{
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+ name: "swig_callback_lto",
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+ heading: "../misc/swig/callback",
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+ fn: func(dt *distTest) error {
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+ cmd := t.addCmd(dt, "misc/swig/callback", t.goTest())
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+ cmd.Env = append(os.Environ(),
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+ "CGO_CFLAGS=-flto",
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+ "CGO_CXXFLAGS=-flto",
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+ "CGO_LDFLAGS=-flto",
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+ )
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+ return nil
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+ },
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+ },
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+ )
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}
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}
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}
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diff --git a/src/cmd/go/testdata/script/cgo_lto2_issue43830.txt b/src/cmd/go/testdata/script/cgo_lto2_issue43830.txt
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new file mode 100644
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index 0000000..e2483ba
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--- /dev/null
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+++ b/src/cmd/go/testdata/script/cgo_lto2_issue43830.txt
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@@ -0,0 +1,33 @@
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+# tests golang.org/issue/43830
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+
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+[!cgo] skip 'skipping test without cgo'
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+[openbsd] env CC='clang'
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+[openbsd] [!exec:clang] skip 'skipping test without clang present'
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+[!openbsd] env CC='gcc'
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+[!openbsd] [!exec:gcc] skip 'skipping test without gcc present'
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+
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+env CGO_CFLAGS='-Wno-ignored-optimization-argument -flto -ffat-lto-objects'
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+
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+go build main.go
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+
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+-- main.go --
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+
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+package main
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+
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+import "fmt"
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+
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+// #include "hello.h"
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+import "C"
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+
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+func main() {
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+ hello := C.hello
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+ fmt.Printf("%v\n", hello)
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+}
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+
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+-- hello.h --
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+
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+#include <stdio.h>
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+
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+void hello(void) {
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+ printf("hello\n");
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+}
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diff --git a/src/cmd/go/testdata/script/cgo_lto_issue43830.txt b/src/cmd/go/testdata/script/cgo_lto_issue43830.txt
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new file mode 100644
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index 0000000..06ab2f3
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--- /dev/null
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+++ b/src/cmd/go/testdata/script/cgo_lto_issue43830.txt
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@@ -0,0 +1,39 @@
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+# tests golang.org/issue/43830
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+
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+[!cgo] skip 'skipping test without cgo'
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+[openbsd] env CC='clang'
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+[openbsd] [!exec:clang] skip 'skipping test without clang present'
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+[!openbsd] env CC='gcc'
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+[!openbsd] [!exec:gcc] skip 'skipping test without gcc present'
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+
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+env CGO_CFLAGS='-Wno-ignored-optimization-argument -flto -ffat-lto-objects'
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+
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+go build main.go add.go
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+
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+-- main.go --
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+
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+package main
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+
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+/*
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+int c_add(int a, int b) {
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+ return myadd(a, b);
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+}
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+*/
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+import "C"
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+
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+func main() {
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+ println(C.c_add(1, 2))
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+}
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+
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+-- add.go --
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+
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+package main
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+
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+import "C"
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+
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+/* test */
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+
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+//export myadd
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+func myadd(a C.int, b C.int) C.int {
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+ return a + b
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+}
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diff --git a/src/cmd/link/internal/ld/ar.go b/src/cmd/link/internal/ld/ar.go
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index 22f53a4..23915f9 100644
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--- a/src/cmd/link/internal/ld/ar.go
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+++ b/src/cmd/link/internal/ld/ar.go
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@@ -124,6 +124,10 @@
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libgcc := sym.Library{Pkg: "libgcc"}
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h := ldobj(ctxt, f, &libgcc, l, pname, name)
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+ if h.ld == nil {
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+ Errorf(nil, "%s unrecognized object file at offset %d", name, off)
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+ continue
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+ }
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f.MustSeek(h.off, 0)
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h.ld(ctxt, f, h.pkg, h.length, h.pn)
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}
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diff --git a/src/cmd/link/internal/ld/config.go b/src/cmd/link/internal/ld/config.go
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index ae0d752..20f1d0b 100644
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--- a/src/cmd/link/internal/ld/config.go
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+++ b/src/cmd/link/internal/ld/config.go
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@@ -241,6 +241,10 @@
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return true, "dynamically linking with a shared library"
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}
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+ if unknownObjFormat {
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+ return true, "some input objects have an unrecognized file format"
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+ }
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+
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return false, ""
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}
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@@ -248,7 +252,7 @@
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//
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// It is called after flags are processed and inputs are processed,
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// so the ctxt.LinkMode variable has an initial value from the -linkmode
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-// flag and the iscgo externalobj variables are set.
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+// flag and the iscgo, externalobj, and unknownObjFormat variables are set.
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func determineLinkMode(ctxt *Link) {
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extNeeded, extReason := mustLinkExternal(ctxt)
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via := ""
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diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
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index e8f001b..644faeb 100644
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--- a/src/cmd/link/internal/ld/lib.go
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+++ b/src/cmd/link/internal/ld/lib.go
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@@ -343,10 +343,16 @@
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const pkgdef = "__.PKGDEF"
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var (
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- // Set if we see an object compiled by the host compiler that is not
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- // from a package that is known to support internal linking mode.
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+ // externalobj is set to true if we see an object compiled by
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+ // the host compiler that is not from a package that is known
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+ // to support internal linking mode.
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externalobj = false
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- theline string
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+
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+ // unknownObjFormat is set to true if we see an object whose
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+ // format we don't recognize.
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+ unknownObjFormat = false
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+
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+ theline string
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)
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func Lflag(ctxt *Link, arg string) {
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@@ -1065,6 +1071,10 @@
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}
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f.MustSeek(h.off, 0)
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+ if h.ld == nil {
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+ Errorf(nil, "%s: unrecognized object file format", h.pn)
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+ continue
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+ }
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h.ld(ctxt, f, h.pkg, h.length, h.pn)
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f.Close()
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}
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@@ -1855,6 +1865,14 @@
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return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
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}
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+ if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
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+ // An unrecognized object is just passed to the external linker.
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+ // If we try to read symbols from this object, we will
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+ // report an error at that time.
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+ unknownObjFormat = true
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+ return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
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+ }
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+
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/* check the header */
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line, err := f.ReadString('\n')
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if err != nil {
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@ -154,6 +154,8 @@ Patch1939923: skip_test_rhbz1939923.patch
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# Port to openssl 3.0
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Patch1952381: rhbz1952381.patch
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Patch1904567: cgo-lto-fix.patch
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# Having documentation separate was broken
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Obsoletes: %{name}-docs < 1.1-4
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@ -253,6 +255,8 @@ Requires: %{name} = %{version}-%{release}
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%patch1939923 -p1
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%patch1904567 -p1
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cp %{SOURCE1} ./src/runtime/
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%build
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@ -566,6 +570,10 @@ cd ..
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%endif
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%changelog
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* Mon Aug 2 2021 Derek Parker <deparker@redhat.com> - 1.16.6-2
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- Backport fix allowing LTO to be enabled on cgo sources
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- Resolves: rhbz#1904567
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* Tue Jul 20 2021 Derek Parker <deparker@redhat.com> - 1.16.6-1
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- Rebase to 1.16.6
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- Resolves: rhbz#1984124
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