cmd/gc: make forward declaration in pure Go package an error

An error during the compilation can be more precise
than an error at link time.

For 'func init', the error happens always: you can't forward
declare an init func because the name gets mangled.

For other funcs, the error happens only with the special
(and never used by hand) -= flag, which tells 6g the
package is pure go.

The go command now passes -= for pure Go packages.

Fixes #3705.

R=ken2
CC=golang-dev
https://golang.org/cl/6996054

diff --git a/doc/progs/error.go b/doc/progs/error.go
index f5073266525cafd1899232d02d7048a9fbe44e2a..57854c5fe5a805758df9ce8b9a7542642b40debe 100644 (file)
--- a/doc/progs/error.go
+++ b/doc/progs/error.go
@@ -20,7 +20,11 @@ import (
 
 type File struct{}
 
-func Open(name string) (file *File, err error)
+func Open(name string) (file *File, err error) {
+       // OMIT
+       panic(1)
+       // STOP OMIT
+}
 
 func openFile() { // OMIT
        f, err := os.Open("filename.ext")

diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 36bc4b2954744c7397ebc9b1798eca59a977ac40..071422367c5cdc3ba0b9e5d603d107dc5b938f95 100644 (file)
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -937,6 +937,7 @@ EXTERN      int     funcdepth;
 EXTERN int     typecheckok;
 EXTERN int     compiling_runtime;
 EXTERN int     compiling_wrappers;
+EXTERN int     pure_go;
 
 EXTERN int     nointerface;
 EXTERN int     fieldtrack_enabled;

diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index eabeaeb646971e7c7d2c2be2af83d65f3d934e76..6fd61d1e34a26810eba5caf233c9f3b1779f83c1 100644 (file)
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -293,8 +293,9 @@ main(int argc, char *argv[])
        if(argc < 1)
                usage();
 
-       // special flag to detect compilation of package runtime
-       compiling_runtime = debug['+'];
+       // special flags used during build.
+       compiling_runtime = debug['+']; // detect compilation of package runtime
+       pure_go = debug['=']; // package is completely go (no C or assembly)
 
        pathname = mal(1000);
        if(getwd(pathname, 999) == 0)

diff --git a/src/cmd/gc/pgen.c b/src/cmd/gc/pgen.c
index 7be254fff173e2cab585e14164cf591afb706620..e388fe6a5eb4e2d27b6acaee4bf7466d40749bd6 100644 (file)
--- a/src/cmd/gc/pgen.c
+++ b/src/cmd/gc/pgen.c
@@ -29,16 +29,19 @@ compile(Node *fn)
                throwreturn = sysfunc("throwreturn");
        }
 
-       if(fn->nbody == nil)
-               return;
+       lno = setlineno(fn);
+
+       if(fn->nbody == nil) {
+               if(pure_go || memcmp(fn->nname->sym->name, "init·", 6) == 0)
+                       yyerror("missing function body", fn);
+               goto ret;
+       }
 
        saveerrors();
 
        // set up domain for labels
        clearlabels();
 
-       lno = setlineno(fn);
-
        curfn = fn;
        dowidth(curfn->type);
 

diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go
index f2d81c02d1e81c71e75a425ec7a9dc5fff7d298d..73dd93fd250c80ce42f129bbe4b8678f087c403c 100644 (file)
--- a/src/cmd/go/build.go
+++ b/src/cmd/go/build.go
@@ -1311,6 +1311,8 @@ func (gcToolchain) linker() string {
        return tool(archChar + "l")
 }
 
+var rsc = flag.Bool("rsc", false, "rsc")
+
 func (gcToolchain) gc(b *builder, p *Package, obj string, importArgs []string, gofiles []string) (ofile string, err error) {
        out := "_go_." + archChar
        ofile = obj + out
@@ -1321,6 +1323,21 @@ func (gcToolchain) gc(b *builder, p *Package, obj string, importArgs []string, g
                gcargs = append(gcargs, "-+")
        }
 
+       // If we're giving the compiler the entire package (no C etc files), tell it that,
+       // so that it can give good error messages about forward declarations.
+       // Exceptions: a few standard packages have forward declarations for
+       // pieces supplied behind-the-scenes by package runtime.
+       extFiles := len(p.CgoFiles) + len(p.CFiles) + len(p.SFiles) + len(p.SysoFiles) + len(p.SwigFiles) + len(p.SwigCXXFiles)
+       if p.Standard {
+               switch p.ImportPath {
+               case "os", "runtime/pprof", "sync", "time":
+                       extFiles++
+               }
+       }
+       if extFiles == 0 {
+               gcargs = append(gcargs, "-=")
+       }
+
        args := stringList(tool(archChar+"g"), "-o", ofile, buildGcflags, gcargs, "-D", p.localPrefix, importArgs)
        for _, f := range gofiles {
                args = append(args, mkAbs(p.Dir, f))