From 193daab9889708f7a20ff46efe0fa4b2bf0468d3 Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Wed, 24 Sep 2014 16:55:26 -0400 Subject: cmd/cc, cmd/ld, runtime: disallow conservative data/bss objects In linker, refuse to write conservative (array of pointers) as the garbage collection type for any variable in the data/bss GC program. In the linker, attach the Go type to an already-read C declaration during dedup. This gives us Go types for C globals for free as long as the cmd/dist-generated Go code contains the declaration. (Most runtime C declarations have a corresponding Go declaration. Both are bss declarations and so the linker dedups them.) In cmd/dist, add a few more C files to the auto-Go-declaration list in order to get Go type information for the C declarations into the linker. In C compiler, mark all non-pointer-containing global declarations and all string data as NOPTR. This allows them to exist in C files without any corresponding Go declaration. Count C function pointers as "non-pointer-containing", since we have no heap-allocated C functions. In runtime, add NOPTR to the remaining pointer-containing declarations, none of which refer to Go heap objects. In runtime, also move os.Args and syscall.envs data into runtime-owned variables. Otherwise, in programs that do not import os or syscall, the runtime variables named os.Args and syscall.envs will be missing type information. I believe that this CL eliminates the final source of conservative GC scanning in non-SWIG Go programs, and therefore... Fixes #909. LGTM=iant R=iant CC=golang-codereviews https://golang.org/cl/149770043 --- src/cmd/cc/dcl.c | 9 ++++++--- src/cmd/cc/lex.c | 2 ++ src/cmd/cgo/out.go | 13 +++++++++++++ src/cmd/dist/buildruntime.c | 2 ++ src/cmd/ld/data.c | 1 + 5 files changed, 24 insertions(+), 3 deletions(-) (limited to 'src/cmd') diff --git a/src/cmd/cc/dcl.c b/src/cmd/cc/dcl.c index 292717d688..117508fd6d 100644 --- a/src/cmd/cc/dcl.c +++ b/src/cmd/cc/dcl.c @@ -30,6 +30,9 @@ #include #include "cc.h" +#include "../ld/textflag.h" + +static int haspointers(Type*); Node* dodecl(void (*f)(int,Type*,Sym*), int c, Type *t, Node *n) @@ -123,7 +126,8 @@ loop: if(dataflag) { s->dataflag = dataflag; dataflag = 0; - } + } else if(s->type != T && !haspointers(s->type)) + s->dataflag = NOPTR; firstbit = 0; n->sym = s; n->type = s->type; @@ -568,9 +572,8 @@ haspointers(Type *t) return 0; case TARRAY: return haspointers(t->link); - case TFUNC: case TIND: - return 1; + return t->link->etype != TFUNC; default: return 0; } diff --git a/src/cmd/cc/lex.c b/src/cmd/cc/lex.c index 55fc36b1e0..7c9f718c09 100644 --- a/src/cmd/cc/lex.c +++ b/src/cmd/cc/lex.c @@ -31,6 +31,7 @@ #include #include "cc.h" #include "y.tab.h" +#include "../ld/textflag.h" #ifndef CPP #define CPP "cpp" @@ -1317,6 +1318,7 @@ cinit(void) t->width = 0; symstring = slookup(".string"); symstring->class = CSTATIC; + symstring->dataflag = NOPTR; symstring->type = t; t = typ(TARRAY, types[TCHAR]); diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go index 6586531ada..2d14f766fc 100644 --- a/src/cmd/cgo/out.go +++ b/src/cmd/cgo/out.go @@ -129,6 +129,7 @@ func (p *Package) writeDefs() { fmt.Fprintf(fc, `extern void *%s __asm__("%s.%s");`, n.Mangle, gccgoSymbolPrefix, n.Mangle) fmt.Fprintf(&gccgoInit, "\t%s = %s%s;\n", n.Mangle, amp, n.C) } else { + fmt.Fprintf(fc, "#pragma dataflag NOPTR /* C pointer, not heap pointer */ \n") fmt.Fprintf(fc, "void *·%s = %s%s;\n", n.Mangle, amp, n.C) } fmt.Fprintf(fc, "\n") @@ -397,6 +398,7 @@ func (p *Package) writeDefsFunc(fc, fgo2 *os.File, n *Name) { // C wrapper calls into gcc, passing a pointer to the argument frame. fmt.Fprintf(fc, "#pragma cgo_import_static %s\n", cname) fmt.Fprintf(fc, "void %s(void*);\n", cname) + fmt.Fprintf(fc, "#pragma dataflag NOPTR\n") fmt.Fprintf(fc, "void *·%s = %s;\n", cname, cname) nret := 0 @@ -1151,20 +1153,31 @@ void *_CMalloc(size_t); const cProlog = ` #include "runtime.h" #include "cgocall.h" +#include "textflag.h" +#pragma dataflag NOPTR static void *cgocall_errno = runtime·cgocall_errno; +#pragma dataflag NOPTR void *·_cgo_runtime_cgocall_errno = &cgocall_errno; +#pragma dataflag NOPTR static void *runtime_gostring = runtime·gostring; +#pragma dataflag NOPTR void *·_cgo_runtime_gostring = &runtime_gostring; +#pragma dataflag NOPTR static void *runtime_gostringn = runtime·gostringn; +#pragma dataflag NOPTR void *·_cgo_runtime_gostringn = &runtime_gostringn; +#pragma dataflag NOPTR static void *runtime_gobytes = runtime·gobytes; +#pragma dataflag NOPTR void *·_cgo_runtime_gobytes = &runtime_gobytes; +#pragma dataflag NOPTR static void *runtime_cmalloc = runtime·cmalloc; +#pragma dataflag NOPTR void *·_cgo_runtime_cmalloc = &runtime_cmalloc; void ·_Cerrno(void*, int32); diff --git a/src/cmd/dist/buildruntime.c b/src/cmd/dist/buildruntime.c index 1257d5b811..bb774e05fc 100644 --- a/src/cmd/dist/buildruntime.c +++ b/src/cmd/dist/buildruntime.c @@ -330,9 +330,11 @@ mkzsys(char *dir, char *file) static char *runtimedefs[] = { "defs.c", "malloc.c", + "mcache.c", "mgc0.c", "proc.c", "parfor.c", + "stack.c", }; // mkzruntimedefs writes zruntime_defs_$GOOS_$GOARCH.h, diff --git a/src/cmd/ld/data.c b/src/cmd/ld/data.c index 71624c3304..9d224d9eb9 100644 --- a/src/cmd/ld/data.c +++ b/src/cmd/ld/data.c @@ -818,6 +818,7 @@ proggenaddsym(ProgGen *g, LSym *s) if(s->gotype == nil && s->size >= PtrSize) { // conservative scan + diag("missing Go type information for global symbol: %s", s->name); if((s->size%PtrSize) || (g->pos%PtrSize)) diag("proggenaddsym: unaligned conservative symbol %s: size=%lld pos=%lld", s->name, s->size, g->pos); -- cgit v1.3