cmd/internal/ld: store the libraries a shared library was linked against in a note
The motivation for this is the innocuous looking test case that is added. This
creates a stack exe -> libdep2.so -> libdep.so -> libruntime.so. The problem
comes from the fact that a function from libdep.so gets inlined all the way
into exe. This (unsurprisingly) means that the object file for exe references
symbols from libdep.so, which means that -ldep needs to be passed when linking
exe and it isn't. The fix is simply to pass it -- there is no harm in passing
it when it's not needed.
The thing is, it's not clear at all in the current code to see how the linker
can know that libdep2 is linked against libdep. It could look through the
DT_NEEDED entries in libdep2 and try to guess which are Go libraries, but it
feels better to be explicit. So this adds another SHT_NOTE section that lists
the shared libraries a shared library was linked against, and makes sure the
complete set of depended upon shared libraries is passed to the external
linker.
Change-Id: I79aa6f98b4db4721d657a7eb7b7f062269bf49e2
Reviewed-on: https://go-review.googlesource.com/10376
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/misc/cgo/testshared/shared_test.go b/misc/cgo/testshared/shared_test.go
index 1d731af..f7a99af 100644
--- a/misc/cgo/testshared/shared_test.go
+++ b/misc/cgo/testshared/shared_test.go
@@ -368,6 +368,21 @@
}
}
+// A Go shared library contains a note indicating which other Go shared libraries it
+// was linked against in an unmapped section.
+func testDepsNote(t *testing.T, f *elf.File, note *note) {
+ if note.section.Flags != 0 {
+ t.Errorf("package list section has flags %v", note.section.Flags)
+ }
+ if isOffsetLoaded(f, note.section.Offset) {
+ t.Errorf("package list section contained in PT_LOAD segment")
+ }
+ // libdep.so just links against the lib containing the runtime.
+ if note.desc != soname {
+ t.Errorf("incorrect dependency list %q", note.desc)
+ }
+}
+
// The shared library contains notes with defined contents; see above.
func TestNotes(t *testing.T) {
goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep")
@@ -382,6 +397,7 @@
}
pkgListNoteFound := false
abiHashNoteFound := false
+ depsNoteFound := false
for _, note := range notes {
if note.name != "GO\x00\x00" {
continue
@@ -399,6 +415,12 @@
}
testABIHashNote(t, f, note)
abiHashNoteFound = true
+ case 3: // ELF_NOTE_GODEPS_TAG
+ if depsNoteFound {
+ t.Error("multiple abi hash notes")
+ }
+ testDepsNote(t, f, note)
+ depsNoteFound = true
}
}
if !pkgListNoteFound {
@@ -407,6 +429,19 @@
if !abiHashNoteFound {
t.Error("abi hash note not found")
}
+ if !depsNoteFound {
+ t.Error("deps note not found")
+ }
+}
+
+// Build a GOPATH package (dep) into a shared library that links against the goroot
+// runtime, another package (dep2) that links against the first, and and an
+// executable that links against dep2.
+func TestTwoGOPathShlibs(t *testing.T) {
+ goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep")
+ goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep2")
+ goCmd(t, "install", "-linkshared", "exe2")
+ run(t, "executable linked to GOPATH library", "./bin/exe2")
}
// Testing rebuilding of shared libraries when they are stale is a bit more
