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cmd/link: when reading symbols from a shared library, allow duplicates when they are both in bss

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This makes the behaviour match what happens when duplicate symbols are read
from regular object files and fixes errors about cgoAlwaysFalse when linking
an executable that uses cgo against a shared library.

Change-Id: Ibb8cd8fe3f7813cde504b7483f1e857868d7e063
Reviewed-on: https://go-review.googlesource.com/11117
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Michael Hudson-Doyle 2015-06-16 13:41:11 +12:00 committed by Ian Lance Taylor
parent b1be121791
commit a5f57d7950
3 changed files with 33 additions and 9 deletions
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7
misc/cgo/testshared/shared_test.go
View File

@ -309,6 +309,13 @@ func TestTrivialExecutable(t *testing.T) {
AssertHasRPath(t, "./bin/trivial", gorootInstallDir)
}
// Build an executable that uses cgo linked against the shared runtime and check it
// runs.
func TestCgoExecutable(t *testing.T) {
goCmd(t, "install", "-linkshared", "execgo")
run(t, "cgo executable", "./bin/execgo")
}
// Build a GOPATH package into a shared library that links against the goroot runtime
// and an executable that links against both.
func TestGopathShlib(t *testing.T) {

8
misc/cgo/testshared/src/execgo/exe.go Normal file
View File

@ -0,0 +1,8 @@
package main
/*
*/
import "C"
func main() {
}

27
src/cmd/link/internal/ld/lib.go
View File

@ -1290,25 +1290,34 @@ func ldshlibsyms(shlib string) {
Diag("cannot read symbols from shared library: %s", libpath)
return
}
for _, s := range syms {
if elf.ST_TYPE(s.Info) == elf.STT_NOTYPE || elf.ST_TYPE(s.Info) == elf.STT_SECTION {
for _, elfsym := range syms {
if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
continue
}
lsym := Linklookup(Ctxt, s.Name, 0)
lsym := Linklookup(Ctxt, elfsym.Name, 0)
if lsym.Type != 0 && lsym.Type != obj.SDYNIMPORT && lsym.Dupok == 0 {
Diag(
"Found duplicate symbol %s reading from %s, first found in %s",
s.Name, shlib, lsym.File)
if (lsym.Type != obj.SBSS && lsym.Type != obj.SNOPTRBSS) || len(lsym.R) != 0 || len(lsym.P) != 0 || f.Sections[elfsym.Section].Type != elf.SHT_NOBITS {
Diag("Found duplicate symbol %s reading from %s, first found in %s", elfsym.Name, shlib, lsym.File)
}
if lsym.Size > int64(elfsym.Size) {
// If the existing symbol is a BSS value that is
// larger than the one read from the shared library,
// keep references to that. Conversely, if the
// version from the shared libray is larger, we want
// to make all references be to that.
continue
}
}
lsym.Type = obj.SDYNIMPORT
lsym.ElfType = elf.ST_TYPE(s.Info)
if s.Section != elf.SHN_UNDEF {
lsym.ElfType = elf.ST_TYPE(elfsym.Info)
lsym.Size = int64(elfsym.Size)
if elfsym.Section != elf.SHN_UNDEF {
// Set .File for the library that actually defines the symbol.
lsym.File = libpath
// The decodetype_* functions in decodetype.go need access to
// the type data.
if strings.HasPrefix(lsym.Name, "type.") && !strings.HasPrefix(lsym.Name, "type..") {
lsym.P = readelfsymboldata(f, &s)
lsym.P = readelfsymboldata(f, &elfsym)
}
}
}