cgo: use slash-free relative paths for .so references

The Makefile and cgo now rewrite / to _ when creating the path.
The .so for gosqlite.googlecode.com/hg/sqlite is named
cgo_gosqlite.googlecode.com_hg_sqlite.so, and then 6l and 8l
both include a default rpath of $GOROOT/pkg/$GOOS_$GOARCH.
This should make it easier to move binaries from one system
to another.

Fixes #857.

R=iant, r
CC=golang-dev
https://golang.org/cl/1700048

src/Make.pkg

@@ -31,11 +31,12 @@ INSTALLFILES+=$(pkgdir)/$(TARG).a
 # The rest of the cgo rules are below, but these variable updates
 # must be done here so they apply to the main rules.
 ifdef CGOFILES
+CGOTARG=cgo_$(subst /,_,$(TARG))
 GOFILES+=$(patsubst %.go,%.cgo1.go,$(CGOFILES))
 GOFILES+=_cgo_gotypes.go
 OFILES+=_cgo_defun.$O
 GCC_OFILES=$(patsubst %.go,%.cgo2.o,$(CGOFILES))
-INSTALLFILES+=$(pkgdir)/$(TARG).so
+INSTALLFILES+=$(pkgdir)/$(CGOTARG).so
 endif
 
 PREREQ+=$(patsubst %,%.make,$(DEPS))
@@ -146,7 +147,7 @@ _cgo_defun.$O: _cgo_defun.c
 _cgo_.so: $(GCC_OFILES) $(CGO_DEPS)
 	gcc $(_CGO_CFLAGS_$(GOARCH)) -o $@ $(GCC_OFILES) $(CGO_LDFLAGS)  $(_CGO_LDFLAGS_$(GOOS))
 
-$(pkgdir)/$(TARG).so: _cgo_.so
+$(pkgdir)/$(CGOTARG).so: _cgo_.so
 	@test -d $(QUOTED_GOROOT)/pkg && mkdir -p $(pkgdir)/$(dir)
 	cp _cgo_.so "$@"
 

src/cmd/5l/obj.c

@@ -146,6 +146,8 @@ main(int argc, char *argv[])
 		usage();
 
 	libinit();
+	if(rpath == nil)
+		rpath = smprint("%s/pkg/%s_%s", goroot, goos, goarch);
 
 	if(!debug['9'] && !debug['U'] && !debug['B'])
 		debug[DEFAULT] = 1;

src/cmd/6l/obj.c

@@ -138,6 +138,8 @@ main(int argc, char *argv[])
 		usage();
 
 	libinit();
+	if(rpath == nil)
+		rpath = smprint("%s/pkg/%s_%s", goroot, goos, goarch);
 
 	if(HEADTYPE == -1) {
 		HEADTYPE = 2;

src/cmd/8l/obj.c

@@ -175,6 +175,8 @@ main(int argc, char *argv[])
 	}
 
 	libinit();
+	if(rpath == nil)
+		rpath = smprint("%s/pkg/%s_%s", goroot, goos, goarch);
 
 	switch(HEADTYPE) {
 	default:

src/cmd/cgo/out.go

@@ -21,6 +21,13 @@ func creat(name string) *os.File {
 	return f
 }
 
+func slashToUnderscore(c int) int {
+	if c == '/' {
+		c = '_'
+	}
+	return c
+}
+
 // writeDefs creates output files to be compiled by 6g, 6c, and gcc.
 // (The comments here say 6g and 6c but the code applies to the 8 and 5 tools too.)
 func (p *Prog) writeDefs() {
@@ -30,6 +37,15 @@ func (p *Prog) writeDefs() {
 		path = pkgroot + "/" + path
 	}
 
+	// The path for the shared object is slash-free so that ELF loaders
+	// will treat it as a relative path.  We rewrite slashes to underscores.
+	sopath := "cgo_" + strings.Map(slashToUnderscore, p.PackagePath)
+	soprefix := ""
+	if os.Getenv("GOOS") == "darwin" {
+		// OS X requires its own prefix for a relative path
+		soprefix = "@rpath/"
+	}
+
 	fgo2 := creat("_cgo_gotypes.go")
 	fc := creat("_cgo_defun.c")
 
@@ -48,10 +64,10 @@ func (p *Prog) writeDefs() {
 	}
 	fmt.Fprintf(fgo2, "type _C_void [0]byte\n")
 
-	fmt.Fprintf(fc, cProlog, pkgroot, pkgroot, pkgroot, pkgroot, pkgroot)
+	fmt.Fprintf(fc, cProlog, soprefix, soprefix, soprefix, soprefix, soprefix)
 
 	for name, def := range p.Vardef {
-		fmt.Fprintf(fc, "#pragma dynimport ·_C_%s %s \"%s.so\"\n", name, name, path)
+		fmt.Fprintf(fc, "#pragma dynimport ·_C_%s %s \"%s%s.so\"\n", name, name, soprefix, sopath)
 		fmt.Fprintf(fgo2, "var _C_%s ", name)
 		printer.Fprint(fgo2, &ast.StarExpr{X: def.Go})
 		fmt.Fprintf(fgo2, "\n")
@@ -130,7 +146,7 @@ func (p *Prog) writeDefs() {
 
 		// C wrapper calls into gcc, passing a pointer to the argument frame.
 		// Also emit #pragma to get a pointer to the gcc wrapper.
-		fmt.Fprintf(fc, "#pragma dynimport _cgo_%s _cgo_%s \"%s.so\"\n", name, name, path)
+		fmt.Fprintf(fc, "#pragma dynimport _cgo_%s _cgo_%s \"%s%s.so\"\n", name, name, soprefix, sopath)
 		fmt.Fprintf(fc, "void (*_cgo_%s)(void*);\n", name)
 		fmt.Fprintf(fc, "\n")
 		fmt.Fprintf(fc, "void\n")
@@ -564,11 +580,11 @@ const cProlog = `
 #include "runtime.h"
 #include "cgocall.h"
 
-#pragma dynimport initcgo initcgo "%s/libcgo.so"
-#pragma dynimport libcgo_thread_start libcgo_thread_start "%s/libcgo.so"
-#pragma dynimport libcgo_set_scheduler libcgo_set_scheduler "%s/libcgo.so"
-#pragma dynimport _cgo_malloc _cgo_malloc "%s/libcgo.so"
-#pragma dynimport _cgo_free _cgo_free "%s/libcgo.so"
+#pragma dynimport initcgo initcgo "%slibcgo.so"
+#pragma dynimport libcgo_thread_start libcgo_thread_start "%slibcgo.so"
+#pragma dynimport libcgo_set_scheduler libcgo_set_scheduler "%slibcgo.so"
+#pragma dynimport _cgo_malloc _cgo_malloc "%slibcgo.so"
+#pragma dynimport _cgo_free _cgo_free "%slibcgo.so"
 
 void
 ·_C_GoString(int8 *p, String s)

src/cmd/ld/macho.c

@@ -441,6 +441,7 @@ asmbmacho(vlong symdatva, vlong symo)
 	vlong v, w;
 	vlong va;
 	int a, i, ptrsize;
+	char *pkgroot;
 	MachoHdr *mh;
 	MachoSect *msect;
 	MachoSeg *ms;
@@ -584,6 +585,12 @@ asmbmacho(vlong symdatva, vlong symo)
 		ml->data[0] = 12;	/* offset to string */
 		strcpy((char*)&ml->data[1], "/usr/lib/dyld");
 
+		if(ndylib > 0) {	/* add reference to where .so files are installed */
+			pkgroot = smprint("%s/pkg/%s_%s", goroot, goos, goarch);
+			ml = newMachoLoad(0x80000000 | 0x1c, 1+(strlen(pkgroot)+1+7)/8*2);	/* LC_RPATH */
+			ml->data[0] = 12;	/* offset of string from beginning of load */
+			strcpy((char*)&ml->data[1], pkgroot);
+		}
 		for(i=0; i<ndylib; i++) {
 			ml = newMachoLoad(12, 4+(strlen(dylib[i])+1+7)/8*2);	/* LC_LOAD_DYLIB */
 			ml->data[0] = 24;	/* offset of string from beginning of load */