cmd/cgo: split cgo_export into cgo_export_static and cgo_export_dynamic

Also emit cgo_ldflag pragmas.

R=golang-dev, remyoudompheng, iant
CC=golang-dev
https://golang.org/cl/7530043

src/cmd/cc/dpchk.c

@@ -692,22 +692,24 @@ pragcgo(char *verb)
 		goto out;
 	}	
 	
-	if(strcmp(verb, "cgo_export") == 0 || strcmp(verb, "dynexport") == 0) {
+	if(strcmp(verb, "dynexport") == 0)
+		verb = "cgo_export_dynamic";
+	if(strcmp(verb, "cgo_export_static") == 0 || strcmp(verb, "cgo_export_dynamic") == 0) {
 		local = getimpsym();
 		if(local == nil)
 			goto err2;
 		if(!more()) {
-			fmtprint(&pragcgobuf, "cgo_export %q\n", local->name);
+			fmtprint(&pragcgobuf, "%s %q\n", verb, local->name);
 			goto out;
 		}
 		remote = getimpsym();
 		if(remote == nil)
 			goto err2;
-		fmtprint(&pragcgobuf, "cgo_export %q %q\n", local->name, remote->name);
+		fmtprint(&pragcgobuf, "%s %q %q\n", verb, local->name, remote->name);
 		goto out;
 	
 	err2:
-		yyerror("usage: #pragma cgo_export local [remote]");
+		yyerror("usage: #pragma %s local [remote]", verb);
 		goto out;
 	}
 	
@@ -749,6 +751,18 @@ pragcgo(char *verb)
 		goto out;
 	}
 	
+	if(strcmp(verb, "cgo_ldflag") == 0) {
+		p = getquoted();
+		if(p == nil)
+			goto err5;
+		fmtprint(&pragcgobuf, "cgo_ldflag %q\n", p);
+		goto out;
+
+	err5:
+		yyerror("usage: #pragma cgo_ldflag \"arg\"");
+		goto out;
+	}
+	
 out:
 	while(getnsc() != '\n')
 		;

src/cmd/cgo/doc.go

@@ -484,16 +484,16 @@ The directives are:
 	Example:
 	#pragma cgo_dynamic_linker "/lib/ld-linux.so.2"
 
-#pragma cgo_export <local> <remote>
+#pragma cgo_export_dynamic <local> <remote>
 
-	In both internal and external linking modes, put the Go symbol
+	In internal linking mode, put the Go symbol
 	named <local> into the program's exported symbol table as
 	<remote>, so that C code can refer to it by that name. This
 	mechanism makes it possible for C code to call back into Go or
 	to share Go's data.
 
 	For compatibility with current versions of SWIG,
-	#pragma dynexport is an alias for #pragma cgo_export.
+	#pragma dynexport is an alias for #pragma cgo_export_dynamic.
 
 #pragma cgo_import_static <local>
 
@@ -505,6 +505,14 @@ The directives are:
 	Example:
 	#pragma cgo_import_static puts_wrapper
 
+#pragma cgo_export_static <local> <remote>
+
+	In external linking mode, put the Go symbol
+	named <local> into the program's exported symbol table as
+	<remote>, so that C code can refer to it by that name. This
+	mechanism makes it possible for C code to call back into Go or
+	to share Go's data.
+
 #pragma cgo_ldflag "<arg>"
 
 	In external linking mode, invoke the host linker (usually gcc)

src/cmd/cgo/gcc.go

@@ -139,11 +139,7 @@ NextLine:
 // addToFlag appends args to flag.  All flags are later written out onto the
 // _cgo_flags file for the build system to use.
 func (p *Package) addToFlag(flag string, args []string) {
-	if oldv, ok := p.CgoFlags[flag]; ok {
-		p.CgoFlags[flag] = oldv + " " + strings.Join(args, " ")
-	} else {
-		p.CgoFlags[flag] = strings.Join(args, " ")
-	}
+	p.CgoFlags[flag] = append(p.CgoFlags[flag], args...)
 	if flag == "CFLAGS" {
 		// We'll also need these when preprocessing for dwarf information.
 		p.GccOptions = append(p.GccOptions, args...)

src/cmd/cgo/main.go

@@ -33,7 +33,7 @@ type Package struct {
 	PtrSize     int64
 	IntSize     int64
 	GccOptions  []string
-	CgoFlags    map[string]string // #cgo flags (CFLAGS, LDFLAGS)
+	CgoFlags    map[string][]string // #cgo flags (CFLAGS, LDFLAGS)
 	Written     map[string]bool
 	Name        map[string]*Name // accumulated Name from Files
 	ExpFunc     []*ExpFunc       // accumulated ExpFunc from Files
@@ -312,7 +312,7 @@ func newPackage(args []string) *Package {
 		PtrSize:    ptrSize,
 		IntSize:    intSize,
 		GccOptions: gccOptions,
-		CgoFlags:   make(map[string]string),
+		CgoFlags:   make(map[string][]string),
 		Written:    make(map[string]bool),
 	}
 	return p

src/cmd/cgo/out.go

@@ -31,7 +31,12 @@ func (p *Package) writeDefs() {
 
 	fflg := creat(*objDir + "_cgo_flags")
 	for k, v := range p.CgoFlags {
-		fmt.Fprintf(fflg, "_CGO_%s=%s\n", k, v)
+		fmt.Fprintf(fflg, "_CGO_%s=%s\n", k, strings.Join(v, " "))
+		if k == "LDFLAGS" {
+			for _, arg := range v {
+				fmt.Fprintf(fc, "#pragma cgo_ldflag %q\n", arg)
+			}
+		}
 	}
 	fflg.Close()
 
@@ -100,6 +105,7 @@ func (p *Package) writeDefs() {
 			fmt.Fprintf(fm, "extern char %s[];\n", n.C)
 			fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C)
 
+			fmt.Fprintf(fc, "#pragma cgo_import_static %s\n", n.C)
 			fmt.Fprintf(fc, "extern byte *%s;\n", n.C)
 
 			cVars[n.C] = true
@@ -651,8 +657,9 @@ func (p *Package) writeExports(fgo2, fc, fm *os.File) {
 		if fn.Recv != nil {
 			goname = "_cgoexpwrap" + cPrefix + "_" + fn.Recv.List[0].Names[0].Name + "_" + goname
 		}
-		fmt.Fprintf(fc, "#pragma cgo_export %s\n", goname)
+		fmt.Fprintf(fc, "#pragma cgo_export_dynamic %s\n", goname)
 		fmt.Fprintf(fc, "extern void ·%s();\n\n", goname)
+		fmt.Fprintf(fc, "#pragma cgo_export_static _cgoexp%s_%s\n", cPrefix, exp.ExpName)
 		fmt.Fprintf(fc, "#pragma textflag 7\n") // no split stack, so no use of m or g
 		fmt.Fprintf(fc, "void\n")
 		fmt.Fprintf(fc, "_cgoexp%s_%s(void *a, int32 n)\n", cPrefix, exp.ExpName)

src/cmd/ld/go.c

@@ -487,7 +487,9 @@ loadcgo(char *file, char *pkg, char *p, int n)
 			continue;
 		}
 
-		if(strcmp(f[0], "cgo_export") == 0) {
+		// TODO: cgo_export_static
+
+		if(strcmp(f[0], "cgo_export_dynamic") == 0) {
 			if(nf < 2 || nf > 3)
 				goto err;
 			local = f[1];
@@ -501,13 +503,17 @@ loadcgo(char *file, char *pkg, char *p, int n)
 				fprint(2, "%s: symbol is both imported and exported: %s\n", argv0, local);
 				nerrors++;
 			}
-			s->dynimpname = remote;
 			s->dynexport = 1;
-
-			if(ndynexp%32 == 0)
-				dynexp = realloc(dynexp, (ndynexp+32)*sizeof dynexp[0]);
-			dynexp[ndynexp++] = s;
-
+			if(s->dynimpname == nil) {
+				s->dynimpname = remote;
+				if(ndynexp%32 == 0)
+					dynexp = realloc(dynexp, (ndynexp+32)*sizeof dynexp[0]);
+				dynexp[ndynexp++] = s;
+			} else if(strcmp(s->dynimpname, remote) != 0) {
+				fprint(2, "%s: conflicting cgo_export directives: %s as %s and %s\n", argv0, s->name, s->dynimpname, remote);
+				nerrors++;
+				return;
+			}
 			if(local != f[1])
 				free(local);
 			continue;
@@ -528,6 +534,15 @@ loadcgo(char *file, char *pkg, char *p, int n)
 			}
 			continue;
 		}
+		
+		if(strcmp(f[0], "cgo_ldflag") == 0) {
+			if(nf != 2)
+				goto err;
+			if(nldflag%32 == 0)
+				ldflag = realloc(ldflag, (nldflag+32)*sizeof ldflag[0]);
+			ldflag[nldflag++] = strdup(f[1]);
+			continue;
+		}
 	}
 	free(p0);
 	return;

src/cmd/ld/lib.h

@@ -138,6 +138,8 @@ EXTERN	char*	outfile;
 EXTERN	int32	nsymbol;
 EXTERN	char*	thestring;
 EXTERN	int	ndynexp;
+EXTERN	int	nldflag;
+EXTERN	char**	ldflag;
 EXTERN	int	havedynamic;
 EXTERN	int	iscgo;
 EXTERN	int	isobj;