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cmd/link: allow symbols from .a files to override those from .so files

Browse source 
https://golang.org/s/execmodes defines rules for how multiple codes of a go
package work when they end up in the address space of a single process, but
currently the linker blows up in this situation. Fix that by loading all .a
files before any .so files and ignoring duplicate symbols found when loading
shared libraries.

I know this is very very late for 1.6 but at least it should clearly not have
any effect when shared libraries are not in use.

Change-Id: I512ac912937e7502ff58eb5628b658ecce3c38e5
Reviewed-on: https://go-review.googlesource.com/18714
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Michael Hudson-Doyle 2016-01-20 15:31:26 +13:00
parent 97266969d8
commit cd9fc3ebfb
5 changed files with 54 additions and 18 deletions
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36
src/cmd/link/internal/ld/lib.go
View file

@ -504,17 +504,24 @@ func loadlib() {
var i int
for i = 0; i < len(Ctxt.Library); i++ {
if Debug['v'] > 1 {
fmt.Fprintf(&Bso, "%5.2f autolib: %s (from %s)\n", obj.Cputime(), Ctxt.Library[i].File, Ctxt.Library[i].Objref)
}
iscgo = iscgo || Ctxt.Library[i].Pkg == "runtime/cgo"
if Ctxt.Library[i].Shlib != "" {
ldshlibsyms(Ctxt.Library[i].Shlib)
} else {
if Ctxt.Library[i].Shlib == "" {
if Debug['v'] > 1 {
fmt.Fprintf(&Bso, "%5.2f autolib: %s (from %s)\n", obj.Cputime(), Ctxt.Library[i].File, Ctxt.Library[i].Objref)
}
objfile(Ctxt.Library[i])
}
}
for i = 0; i < len(Ctxt.Library); i++ {
if Ctxt.Library[i].Shlib != "" {
if Debug['v'] > 1 {
fmt.Fprintf(&Bso, "%5.2f autolib: %s (from %s)\n", obj.Cputime(), Ctxt.Library[i].Shlib, Ctxt.Library[i].Objref)
}
ldshlibsyms(Ctxt.Library[i].Shlib)
}
}
if Linkmode == LinkAuto {
if iscgo && externalobj {
Linkmode = LinkExternal
@ -1458,18 +1465,11 @@ func ldshlibsyms(shlib string) {
continue
}
lsym := Linklookup(Ctxt, elfsym.Name, 0)
if lsym.Type != 0 && lsym.Type != obj.SDYNIMPORT && lsym.Dupok == 0 {
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
}
// Because loadlib above loads all .a files before loading any shared
// libraries, any symbols we find that duplicate symbols already
// loaded should be ignored (the symbols from the .a files "win").
if lsym.Type != 0 {
continue
}
lsym.Type = obj.SDYNIMPORT
lsym.ElfType = elf.ST_TYPE(elfsym.Info)