cmd/gc: reject non-Go constants Expressions involving nil, even if they can be evaluated at compile time, do not count as Go constants and cannot be used in const initializers. Fixes #4673. Fixes #4680. R=ken2 CC=golang-dev https://golang.org/cl/7278043
diff --git a/src/cmd/gc/const.c b/src/cmd/gc/const.c index f82ba94..83e62bd 100644 --- a/src/cmd/gc/const.c +++ b/src/cmd/gc/const.c
@@ -78,6 +78,7 @@ if(!explicit && !isideal(n->type)) return; + if(n->op == OLITERAL) { nn = nod(OXXX, N, N); *nn = *n; @@ -953,10 +954,6 @@ *n = *nl; // restore value of n->orig. n->orig = norig; - if(norig->op == OCONV) { - dump("N", n); - dump("NORIG", norig); - } n->val = v; // check range. @@ -1449,3 +1446,132 @@ mpsubfltflt(&v->imag, &ad); // bc-ad mpdivfltflt(&v->imag, &cc_plus_dd); // (bc+ad)/(cc+dd) } + +static int hascallchan(Node*); + +// Is n a Go language constant (as opposed to a compile-time constant)? +// Expressions derived from nil, like string([]byte(nil)), while they +// may be known at compile time, are not Go language constants. +// Only called for expressions known to evaluated to compile-time +// constants. +int +isgoconst(Node *n) +{ + Node *l; + Type *t; + + if(n->orig != N) + n = n->orig; + + switch(n->op) { + case OADD: + case OADDSTR: + case OAND: + case OANDAND: + case OANDNOT: + case OCOM: + case ODIV: + case OEQ: + case OGE: + case OGT: + case OLE: + case OLSH: + case OLT: + case OMINUS: + case OMOD: + case OMUL: + case ONE: + case ONOT: + case OOR: + case OOROR: + case OPLUS: + case ORSH: + case OSUB: + case OXOR: + case OCONV: + case OIOTA: + case OCOMPLEX: + case OREAL: + case OIMAG: + if(isgoconst(n->left) && (n->right == N || isgoconst(n->right))) + return 1; + break; + + case OLEN: + case OCAP: + l = n->left; + if(isgoconst(l)) + return 1; + // Special case: len/cap is constant when applied to array or + // pointer to array when the expression does not contain + // function calls or channel receive operations. + t = l->type; + if(t != T && isptr[t->etype]) + t = t->type; + if(isfixedarray(t) && !hascallchan(l)) + return 1; + break; + + case OLITERAL: + if(n->val.ctype != CTNIL) + return 1; + break; + + case ONAME: + l = n->sym->def; + if(l->op == OLITERAL && n->val.ctype != CTNIL) + return 1; + break; + + case ONONAME: + if(n->sym->def != N && n->sym->def->op == OIOTA) + return 1; + break; + + case OCALL: + // Only constant calls are unsafe.Alignof, Offsetof, and Sizeof. + l = n->left; + while(l->op == OPAREN) + l = l->left; + if(l->op != ONAME || l->sym->pkg != unsafepkg) + break; + if(strcmp(l->sym->name, "Alignof") == 0 || + strcmp(l->sym->name, "Offsetof") == 0 || + strcmp(l->sym->name, "Sizeof") == 0) + return 1; + break; + } + + //dump("nonconst", n); + return 0; +} + +static int +hascallchan(Node *n) +{ + NodeList *l; + + if(n == N) + return 0; + switch(n->op) { + case OCALL: + case OCALLFUNC: + case OCALLMETH: + case OCALLINTER: + case ORECV: + return 1; + } + + if(hascallchan(n->left) || + hascallchan(n->right)) + return 1; + + for(l=n->list; l; l=l->next) + if(hascallchan(l->n)) + return 1; + for(l=n->rlist; l; l=l->next) + if(hascallchan(l->n)) + return 1; + + return 0; +}
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h index 9d2ff4d..1f8446b 100644 --- a/src/cmd/gc/go.h +++ b/src/cmd/gc/go.h
@@ -997,6 +997,7 @@ void defaultlit2(Node **lp, Node **rp, int force); void evconst(Node *n); int isconst(Node *n, int ct); +int isgoconst(Node *n); Node* nodcplxlit(Val r, Val i); Node* nodlit(Val v); long nonnegconst(Node *n);
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c index afbdd0c..01e738b 100644 --- a/src/cmd/gc/subr.c +++ b/src/cmd/gc/subr.c
@@ -840,6 +840,7 @@ default: m = nod(OXXX, N, N); *m = *n; + m->orig = m; m->left = treecopy(n->left); m->right = treecopy(n->right); m->list = listtreecopy(n->list);
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c index 3771613..1bfa0cc 100644 --- a/src/cmd/gc/typecheck.c +++ b/src/cmd/gc/typecheck.c
@@ -1336,6 +1336,9 @@ case OCONV: doconv: ok |= Erv; + l = nod(OXXX, N, N); + n->orig = l; + *l = *n; typecheck(&n->left, Erv | (top & (Eindir | Eiota))); convlit1(&n->left, n->type, 1); if((t = n->left->type) == T || n->type == T) @@ -3007,14 +3010,14 @@ yyerror("xxx"); } typecheck(&e, Erv | Eiota); - if(e->type != T && e->op != OLITERAL) { - yyerror("const initializer must be constant"); - goto ret; - } if(isconst(e, CTNIL)) { yyerror("const initializer cannot be nil"); goto ret; } + if(e->type != T && e->op != OLITERAL || !isgoconst(e)) { + yyerror("const initializer %N is not a constant", e); + goto ret; + } t = n->type; if(t != T) { if(!okforconst[t->etype]) {
diff --git a/test/const1.go b/test/const1.go index 1580b76..a170ce9 100644 --- a/test/const1.go +++ b/test/const1.go
@@ -9,6 +9,8 @@ package main +import "unsafe" + type I interface{} const ( @@ -86,3 +88,7 @@ } const ptr = nil // ERROR "const.*nil" +const _ = string([]byte(nil)) // ERROR "is not a constant" +const _ = uintptr(unsafe.Pointer((*int)(nil))) // ERROR "is not a constant" +const _ = unsafe.Pointer((*int)(nil)) // ERROR "cannot be nil" +const _ = (*int)(nil) // ERROR "cannot be nil"
diff --git a/test/const5.go b/test/const5.go index d0eed13..87fe33a 100644 --- a/test/const5.go +++ b/test/const5.go
@@ -24,10 +24,10 @@ n2 = len(m[""]) n3 = len(s[10]) - n4 = len(f()) // ERROR "must be constant|is not constant" - n5 = len(<-c) // ERROR "must be constant|is not constant" + n4 = len(f()) // ERROR "is not a constant|is not constant" + n5 = len(<-c) // ERROR "is not a constant|is not constant" - n6 = cap(f()) // ERROR "must be constant|is not constant" - n7 = cap(<-c) // ERROR "must be constant|is not constant" + n6 = cap(f()) // ERROR "is not a constant|is not constant" + n7 = cap(<-c) // ERROR "is not a constant|is not constant" )
diff --git a/test/fixedbugs/bug297.go b/test/fixedbugs/bug297.go index b5dfa8d..ee2ff92 100644 --- a/test/fixedbugs/bug297.go +++ b/test/fixedbugs/bug297.go
@@ -11,5 +11,5 @@ type ByteSize float64 const ( _ = iota; // ignore first value by assigning to blank identifier - KB ByteSize = 1<<(10*X) // ERROR "undefined" "as type ByteSize" + KB ByteSize = 1<<(10*X) // ERROR "undefined" "is not a constant|as type ByteSize" )
diff --git a/test/fixedbugs/issue4097.go b/test/fixedbugs/issue4097.go index 2c999a8..fa942c9 100644 --- a/test/fixedbugs/issue4097.go +++ b/test/fixedbugs/issue4097.go
@@ -7,5 +7,5 @@ package foo var s [][10]int -const m = len(s[len(s)-1]) // ERROR "must be constant" +const m = len(s[len(s)-1]) // ERROR "is not a constant"
diff --git a/test/fixedbugs/issue4654.go b/test/fixedbugs/issue4654.go index 4c5a55c..170594e 100644 --- a/test/fixedbugs/issue4654.go +++ b/test/fixedbugs/issue4654.go
@@ -48,7 +48,7 @@ defer recover() // ok int(0) // ERROR "int\(0\) evaluated but not used" - string([]byte("abc")) // ERROR "string\(\[\]byte literal\) evaluated but not used" + string([]byte("abc")) // ERROR "string\(.*\) evaluated but not used" append(x, 1) // ERROR "not used" cap(x) // ERROR "not used"
diff --git a/test/run.go b/test/run.go index bc545df..36c8b7a 100644 --- a/test/run.go +++ b/test/run.go
@@ -683,6 +683,7 @@ continue } matched := false + n := len(out) for _, errmsg := range errmsgs { if we.re.MatchString(errmsg) { matched = true @@ -691,7 +692,7 @@ } } if !matched { - errs = append(errs, fmt.Errorf("%s:%d: no match for %q in%s", we.file, we.lineNum, we.reStr, strings.Join(out, "\n"))) + errs = append(errs, fmt.Errorf("%s:%d: no match for %#q in:\n\t%s", we.file, we.lineNum, we.reStr, strings.Join(out[n:], "\n\t"))) continue } } @@ -758,7 +759,7 @@ all := m[1] mm := errQuotesRx.FindAllStringSubmatch(all, -1) if mm == nil { - log.Fatalf("invalid errchk line in %s: %s", t.goFileName(), line) + log.Fatalf("%s:%d: invalid errchk line: %s", t.goFileName(), lineNum, line) } for _, m := range mm { rx := lineRx.ReplaceAllStringFunc(m[1], func(m string) string { @@ -772,10 +773,14 @@ } return fmt.Sprintf("%s:%d", short, n) }) - filterPattern := fmt.Sprintf(`^(\w+/)?%s:%d[:[]`, short, lineNum) + re, err := regexp.Compile(rx) + if err != nil { + log.Fatalf("%s:%d: invalid regexp in ERROR line: %v", t.goFileName(), lineNum, err) + } + filterPattern := fmt.Sprintf(`^(\w+/)?%s:%d[:[]`, regexp.QuoteMeta(short), lineNum) errs = append(errs, wantedError{ reStr: rx, - re: regexp.MustCompile(rx), + re: re, filterRe: regexp.MustCompile(filterPattern), lineNum: lineNum, file: short,