commit 9cfcd0c29677e11f76846b006757ff49e05e3d6f (tree)
parent 1ca49b92c650e9b8988a35983e202cdb9c7ba6e7
Author: Andrew Kelley <andrew@ziglang.org>
Date: Thu, 20 Aug 2020 18:35:31 -0400
Merge pull request #6103 from Vexu/extern
Disallow extern variables with initializers.
Diffstat:
13 files changed, 122 insertions(+), 33 deletions(-)
diff --git a/lib/std/c/darwin.zig b/lib/std/c/darwin.zig
@@ -46,10 +46,11 @@ const mach_hdr = if (@sizeOf(usize) == 8) mach_header_64 else mach_header;
/// on this operating system. However when building object files or libraries,
/// the system libc won't be linked until the final executable. So we
/// export a weak symbol here, to be overridden by the real one.
-pub extern "c" var _mh_execute_header: mach_hdr = undefined;
+var dummy_execute_header: mach_hdr = undefined;
+pub extern var _mh_execute_header: mach_hdr;
comptime {
if (std.Target.current.isDarwin()) {
- @export(_mh_execute_header, .{ .name = "_mh_execute_header", .linkage = .Weak });
+ @export(dummy_execute_header, .{ .name = "_mh_execute_header", .linkage = .Weak });
}
}
diff --git a/lib/std/mem.zig b/lib/std/mem.zig
@@ -226,9 +226,19 @@ pub fn zeroes(comptime T: type) T {
.Vector => |info| {
return @splat(info.len, zeroes(info.child));
},
+ .Union => |info| {
+ if (comptime meta.containerLayout(T) == .Extern) {
+ // The C language specification states that (global) unions
+ // should be zero initialized to the first named member.
+ var item: T = undefined;
+ @field(item, info.fields[0].name) = zeroes(@TypeOf(@field(item, info.fields[0].name)));
+ return item;
+ }
+
+ @compileError("Can't set a " ++ @typeName(T) ++ " to zero.");
+ },
.ErrorUnion,
.ErrorSet,
- .Union,
.Fn,
.BoundFn,
.Type,
@@ -317,6 +327,14 @@ test "mem.zeroes" {
for (b.sentinel) |e| {
testing.expectEqual(@as(u8, 0), e);
}
+
+ const C_union = extern union {
+ a: u8,
+ b: u32,
+ };
+
+ var c = zeroes(C_union);
+ testing.expectEqual(@as(u8, 0), c.a);
}
/// Sets a slice to zeroes.
diff --git a/lib/std/special/c.zig b/lib/std/special/c.zig
@@ -40,7 +40,7 @@ comptime {
}
}
-extern var _fltused: c_int = 1;
+var _fltused: c_int = 1;
extern fn main(argc: c_int, argv: [*:null]?[*:0]u8) c_int;
fn wasm_start() callconv(.C) void {
diff --git a/lib/std/special/compiler_rt.zig b/lib/std/special/compiler_rt.zig
@@ -340,7 +340,7 @@ fn __stack_chk_fail() callconv(.C) noreturn {
@panic("stack smashing detected");
}
-extern var __stack_chk_guard: usize = blk: {
+var __stack_chk_guard: usize = blk: {
var buf = [1]u8{0} ** @sizeOf(usize);
buf[@sizeOf(usize) - 1] = 255;
buf[@sizeOf(usize) - 2] = '\n';
diff --git a/src-self-hosted/Module.zig b/src-self-hosted/Module.zig
@@ -324,10 +324,10 @@ pub const Fn = struct {
};
pub const Var = struct {
+ /// if is_extern == true this is undefined
init: Value,
owner_decl: *Decl,
- has_init: bool,
is_extern: bool,
is_mutable: bool,
is_threadlocal: bool,
@@ -1456,7 +1456,11 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
const is_extern = blk: {
const maybe_extern_token = var_decl.getTrailer("extern_export_token") orelse
break :blk false;
- break :blk tree.token_ids[maybe_extern_token] == .Keyword_extern;
+ if (tree.token_ids[maybe_extern_token] != .Keyword_extern) break :blk false;
+ if (var_decl.getTrailer("init_node")) |some| {
+ return self.failNode(&block_scope.base, some, "extern variables have no initializers", .{});
+ }
+ break :blk true;
};
if (var_decl.getTrailer("lib_name")) |lib_name| {
assert(is_extern);
@@ -1569,7 +1573,6 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
new_variable.* = .{
.owner_decl = decl,
.init = value orelse undefined,
- .has_init = value != null,
.is_extern = is_extern,
.is_mutable = is_mutable,
.is_threadlocal = is_threadlocal,
@@ -2440,7 +2443,7 @@ fn analyzeVarRef(self: *Module, scope: *Scope, src: usize, tv: TypedValue) Inner
const variable = tv.val.cast(Value.Payload.Variable).?.variable;
const ty = try self.singlePtrType(scope, src, variable.is_mutable, tv.ty);
- if (!variable.is_mutable and !variable.is_extern and variable.has_init) {
+ if (!variable.is_mutable and !variable.is_extern) {
const val_payload = try scope.arena().create(Value.Payload.RefVal);
val_payload.* = .{ .val = variable.init };
return self.constInst(scope, src, .{
diff --git a/src-self-hosted/translate_c.zig b/src-self-hosted/translate_c.zig
@@ -498,7 +498,7 @@ fn declVisitor(c: *Context, decl: *const ZigClangDecl) Error!void {
_ = try transRecordDecl(c, @ptrCast(*const ZigClangRecordDecl, decl));
},
.Var => {
- return visitVarDecl(c, @ptrCast(*const ZigClangVarDecl, decl));
+ return visitVarDecl(c, @ptrCast(*const ZigClangVarDecl, decl), null);
},
.Empty => {
// Do nothing
@@ -679,12 +679,13 @@ fn visitFnDecl(c: *Context, fn_decl: *const ZigClangFunctionDecl) Error!void {
return addTopLevelDecl(c, fn_name, &proto_node.base);
}
-fn visitVarDecl(c: *Context, var_decl: *const ZigClangVarDecl) Error!void {
- const var_name = try c.str(ZigClangNamedDecl_getName_bytes_begin(@ptrCast(*const ZigClangNamedDecl, var_decl)));
+/// if mangled_name is not null, this var decl was declared in a block scope.
+fn visitVarDecl(c: *Context, var_decl: *const ZigClangVarDecl, mangled_name: ?[]const u8) Error!void {
+ const var_name = mangled_name orelse try c.str(ZigClangNamedDecl_getName_bytes_begin(@ptrCast(*const ZigClangNamedDecl, var_decl)));
if (c.global_scope.sym_table.contains(var_name))
return; // Avoid processing this decl twice
const rp = makeRestorePoint(c);
- const visib_tok = try appendToken(c, .Keyword_pub, "pub");
+ const visib_tok = if (mangled_name) |_| null else try appendToken(c, .Keyword_pub, "pub");
const thread_local_token = if (ZigClangVarDecl_getTLSKind(var_decl) == .None)
null
@@ -701,8 +702,14 @@ fn visitVarDecl(c: *Context, var_decl: *const ZigClangVarDecl) Error!void {
const qual_type = ZigClangVarDecl_getTypeSourceInfo_getType(var_decl);
const storage_class = ZigClangVarDecl_getStorageClass(var_decl);
const is_const = ZigClangQualType_isConstQualified(qual_type);
-
- const extern_tok = if (storage_class == .Extern)
+ const has_init = ZigClangVarDecl_hasInit(var_decl);
+
+ // In C extern variables with initializers behave like Zig exports.
+ // extern int foo = 2;
+ // does the same as:
+ // extern int foo;
+ // int foo = 2;
+ const extern_tok = if (storage_class == .Extern and !has_init)
try appendToken(c, .Keyword_extern, "extern")
else if (storage_class != .Static)
try appendToken(c, .Keyword_export, "export")
@@ -730,7 +737,7 @@ fn visitVarDecl(c: *Context, var_decl: *const ZigClangVarDecl) Error!void {
// If the initialization expression is not present, initialize with undefined.
// If it is an integer literal, we can skip the @as since it will be redundant
// with the variable type.
- if (ZigClangVarDecl_hasInit(var_decl)) {
+ if (has_init) {
eq_tok = try appendToken(c, .Equal, "=");
init_node = if (ZigClangVarDecl_getInit(var_decl)) |expr|
transExprCoercing(rp, &c.global_scope.base, expr, .used, .r_value) catch |err| switch (err) {
@@ -745,7 +752,22 @@ fn visitVarDecl(c: *Context, var_decl: *const ZigClangVarDecl) Error!void {
try transCreateNodeUndefinedLiteral(c);
} else if (storage_class != .Extern) {
eq_tok = try appendToken(c, .Equal, "=");
- init_node = try transCreateNodeIdentifierUnchecked(c, "undefined");
+ // The C language specification states that variables with static or threadlocal
+ // storage without an initializer are initialized to a zero value.
+
+ // @import("std").mem.zeroes(T)
+ const import_fn_call = try c.createBuiltinCall("@import", 1);
+ const std_node = try transCreateNodeStringLiteral(c, "\"std\"");
+ import_fn_call.params()[0] = std_node;
+ import_fn_call.rparen_token = try appendToken(c, .RParen, ")");
+ const inner_field_access = try transCreateNodeFieldAccess(c, &import_fn_call.base, "mem");
+ const outer_field_access = try transCreateNodeFieldAccess(c, inner_field_access, "zeroes");
+
+ const zero_init_call = try c.createCall(outer_field_access, 1);
+ zero_init_call.params()[0] = type_node;
+ zero_init_call.rtoken = try appendToken(c, .RParen, ")");
+
+ init_node = &zero_init_call.base;
}
const linksection_expr = blk: {
@@ -1561,15 +1583,22 @@ fn transDeclStmtOne(
.Var => {
const var_decl = @ptrCast(*const ZigClangVarDecl, decl);
- const thread_local_token = if (ZigClangVarDecl_getTLSKind(var_decl) == .None)
- null
- else
- try appendToken(c, .Keyword_threadlocal, "threadlocal");
const qual_type = ZigClangVarDecl_getTypeSourceInfo_getType(var_decl);
const name = try c.str(ZigClangNamedDecl_getName_bytes_begin(
@ptrCast(*const ZigClangNamedDecl, var_decl),
));
const mangled_name = try block_scope.makeMangledName(c, name);
+
+ switch (ZigClangVarDecl_getStorageClass(var_decl)) {
+ .Extern, .Static => {
+ // This is actually a global variable, put it in the global scope and reference it.
+ // `_ = mangled_name;`
+ try visitVarDecl(rp.c, var_decl, mangled_name);
+ return try maybeSuppressResult(rp, scope, .unused, try transCreateNodeIdentifier(rp.c, mangled_name));
+ },
+ else => {},
+ }
+
const mut_tok = if (ZigClangQualType_isConstQualified(qual_type))
try appendToken(c, .Keyword_const, "const")
else
@@ -1597,7 +1626,6 @@ fn transDeclStmtOne(
.mut_token = mut_tok,
.semicolon_token = semicolon_token,
}, .{
- .thread_local_token = thread_local_token,
.eq_token = eq_token,
.type_node = type_node,
.init_node = init_node,
diff --git a/src/codegen.cpp b/src/codegen.cpp
@@ -292,13 +292,14 @@ static void add_uwtable_attr(CodeGen *g, LLVMValueRef fn_val) {
}
}
-static LLVMLinkage to_llvm_linkage(GlobalLinkageId id) {
+static LLVMLinkage to_llvm_linkage(GlobalLinkageId id, bool is_extern) {
switch (id) {
case GlobalLinkageIdInternal:
return LLVMInternalLinkage;
case GlobalLinkageIdStrong:
return LLVMExternalLinkage;
case GlobalLinkageIdWeak:
+ if (is_extern) return LLVMExternalWeakLinkage;
return LLVMWeakODRLinkage;
case GlobalLinkageIdLinkOnce:
return LLVMLinkOnceODRLinkage;
@@ -521,7 +522,7 @@ static LLVMValueRef make_fn_llvm_value(CodeGen *g, ZigFn *fn) {
}
- LLVMSetLinkage(llvm_fn, to_llvm_linkage(linkage));
+ LLVMSetLinkage(llvm_fn, to_llvm_linkage(linkage, fn->body_node == nullptr));
if (linkage == GlobalLinkageIdInternal) {
LLVMSetUnnamedAddr(llvm_fn, true);
@@ -7962,7 +7963,7 @@ static void do_code_gen(CodeGen *g) {
global_value = LLVMAddGlobal(g->module, get_llvm_type(g, var->var_type), symbol_name);
// TODO debug info for the extern variable
- LLVMSetLinkage(global_value, to_llvm_linkage(linkage));
+ LLVMSetLinkage(global_value, to_llvm_linkage(linkage, true));
maybe_import_dll(g, global_value, GlobalLinkageIdStrong);
LLVMSetAlignment(global_value, var->align_bytes);
LLVMSetGlobalConstant(global_value, var->gen_is_const);
@@ -7975,7 +7976,7 @@ static void do_code_gen(CodeGen *g) {
global_value = var->const_value->llvm_global;
if (exported) {
- LLVMSetLinkage(global_value, to_llvm_linkage(linkage));
+ LLVMSetLinkage(global_value, to_llvm_linkage(linkage, false));
maybe_export_dll(g, global_value, GlobalLinkageIdStrong);
}
if (var->section_name) {
diff --git a/src/parser.cpp b/src/parser.cpp
@@ -680,6 +680,9 @@ static AstNode *ast_parse_top_level_decl(ParseContext *pc, VisibMod visib_mod, B
AstNode *var_decl = ast_parse_var_decl(pc);
if (var_decl != nullptr) {
assert(var_decl->type == NodeTypeVariableDeclaration);
+ if (first->id == TokenIdKeywordExtern && var_decl->data.variable_declaration.expr != nullptr) {
+ ast_error(pc, first, "extern variables have no initializers");
+ }
var_decl->line = first->start_line;
var_decl->column = first->start_column;
var_decl->data.variable_declaration.threadlocal_tok = thread_local_kw;
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
@@ -2,6 +2,12 @@ const tests = @import("tests.zig");
const std = @import("std");
pub fn addCases(cases: *tests.CompileErrorContext) void {
+ cases.addTest("reject extern variables with initializers",
+ \\extern var foo: int = 2;
+ , &[_][]const u8{
+ "tmp.zig:1:1: error: extern variables have no initializers",
+ });
+
cases.addTest("duplicate/unused labels",
\\comptime {
\\ blk: { blk: while (false) {} }
diff --git a/test/run_translated_c.zig b/test/run_translated_c.zig
@@ -3,6 +3,20 @@ const tests = @import("tests.zig");
const nl = std.cstr.line_sep;
pub fn addCases(cases: *tests.RunTranslatedCContext) void {
+ cases.add("static variable in block scope",
+ \\#include <stdlib.h>
+ \\int foo() {
+ \\ static int bar;
+ \\ bar += 1;
+ \\ return bar;
+ \\}
+ \\int main() {
+ \\ foo();
+ \\ foo();
+ \\ if (foo() != 3) abort();
+ \\}
+ , "");
+
cases.add("array initializer",
\\#include <stdlib.h>
\\int main(int argc, char **argv) {
diff --git a/test/standalone/global_linkage/obj1.zig b/test/standalone/global_linkage/obj1.zig
@@ -1,5 +1,5 @@
-extern var internal_integer: usize = 1;
-extern var obj1_integer: usize = 421;
+var internal_integer: usize = 1;
+var obj1_integer: usize = 421;
comptime {
@export(internal_integer, .{ .name = "internal_integer", .linkage = .Internal });
diff --git a/test/standalone/global_linkage/obj2.zig b/test/standalone/global_linkage/obj2.zig
@@ -1,5 +1,5 @@
-extern var internal_integer: usize = 2;
-extern var obj2_integer: usize = 422;
+var internal_integer: usize = 2;
+var obj2_integer: usize = 422;
comptime {
@export(internal_integer, .{ .name = "internal_integer", .linkage = .Internal });
diff --git a/test/translate_c.zig b/test/translate_c.zig
@@ -3,6 +3,20 @@ const std = @import("std");
const CrossTarget = std.zig.CrossTarget;
pub fn addCases(cases: *tests.TranslateCContext) void {
+ cases.add("extern variable in block scope",
+ \\float bar;
+ \\int foo() {
+ \\ _Thread_local static int bar = 2;
+ \\}
+ , &[_][]const u8{
+ \\pub export var bar: f32 = @import("std").mem.zeroes(f32);
+ \\threadlocal var bar_1: c_int = 2;
+ \\pub export fn foo() c_int {
+ \\ _ = bar_1;
+ \\ return 0;
+ \\}
+ });
+
cases.add("missing return stmt",
\\int foo() {}
\\int bar() {
@@ -466,7 +480,7 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
, &[_][]const u8{
\\pub extern var extern_var: c_int;
\\pub const int_var: c_int = 13;
- \\pub export var foo: c_int = undefined;
+ \\pub export var foo: c_int = @import("std").mem.zeroes(c_int);
});
cases.add("const ptr initializer",
@@ -480,8 +494,9 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
\\ static const char v2[] = "2.2.2";
\\}
, &[_][]const u8{
+ \\const v2: [*c]const u8 = "2.2.2";
\\pub export fn foo() void {
- \\ const v2: [*c]const u8 = "2.2.2";
+ \\ _ = v2;
\\}
});
@@ -1327,7 +1342,7 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
\\static char arr1[] = "hello";
\\char arr2[] = "hello";
, &[_][]const u8{
- \\pub extern var arr0: [*c]u8 = "hello";
+ \\pub export var arr0: [*c]u8 = "hello";
\\pub var arr1: [*c]u8 = "hello";
\\pub export var arr2: [*c]u8 = "hello";
});
