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translate-c: allow string literals to be used as char *
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In C the type of string literals is `char *`, so when using them in
a non-const context we have to cast the const away.

Fixes #9126
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@ehaas
ehaas committed Aug 14, 2021
1 parent c2635f9 commit f104d7d
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Showing 3 changed files with 115 additions and 11 deletions.
93 changes: 87 additions & 6 deletions src/translate_c.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -719,6 +719,44 @@ fn transQualTypeMaybeInitialized(c: *Context, scope: *Scope, qt: clang.QualType,
transQualType(c, scope, qt, loc);
}

/// This is used in global scope to convert a string literal `S` to [*c]u8:
/// &(struct {
/// var static: @TypeOf(S.*) = S.*;
/// }).static;
fn stringLiteralToCharStar(c: *Context, scope: *Scope, str: Node) Error!Node {
const var_name = Scope.Block.StaticInnerName;

const derefed = try Tag.deref.create(c.arena, str);
const var_type = try Tag.typeof.create(c.arena, derefed);

const variables = try c.arena.alloc(Node, 1);
variables[0] = try Tag.var_decl.create(c.arena, .{
.is_pub = false,
.is_const = false,
.is_extern = false,
.is_export = false,
.is_threadlocal = false,
.linksection_string = null,
.alignment = null,
.name = var_name,
.type = var_type,
.init = derefed,
});

const anon_struct = try Tag.@"struct".create(c.arena, .{
.layout = .none,
.fields = &.{},
.functions = &.{},
.variables = variables,
});

const member_access = try Tag.field_access.create(c.arena, .{
.lhs = anon_struct,
.field_name = var_name,
});
return Tag.address_of.create(c.arena, member_access);
}

/// if mangled_name is not null, this var decl was declared in a block scope.
fn visitVarDecl(c: *Context, var_decl: *const clang.VarDecl, mangled_name: ?[]const u8) Error!void {
const var_name = mangled_name orelse try c.str(@ptrCast(*const clang.NamedDecl, var_decl).getName_bytes_begin());
Expand Down Expand Up @@ -779,6 +817,8 @@ fn visitVarDecl(c: *Context, var_decl: *const clang.VarDecl, mangled_name: ?[]co
};
if (!qualTypeIsBoolean(qual_type) and isBoolRes(init_node.?)) {
init_node = try Tag.bool_to_int.create(c.arena, init_node.?);
} else if (init_node.?.tag() == .string_literal and qualTypeIsCharStar(qual_type)) {
init_node = try stringLiteralToCharStar(c, scope, init_node.?);
}
} else {
init_node = Tag.undefined_literal.init();
Expand Down Expand Up @@ -1101,9 +1141,10 @@ fn transRecordDecl(c: *Context, scope: *Scope, record_decl: *const clang.RecordD
record_payload.* = .{
.base = .{ .tag = ([2]Tag{ .@"struct", .@"union" })[@boolToInt(is_union)] },
.data = .{
.is_packed = is_packed,
.layout = if (is_packed) .@"packed" else .@"extern",
.fields = try c.arena.dupe(ast.Payload.Record.Field, fields.items),
.functions = try c.arena.dupe(Node, functions.items),
.variables = &.{},
},
};
break :blk Node.initPayload(&record_payload.base);
Expand Down Expand Up @@ -1805,6 +1846,9 @@ fn transDeclStmtOne(
Tag.undefined_literal.init();
if (!qualTypeIsBoolean(qual_type) and isBoolRes(init_node)) {
init_node = try Tag.bool_to_int.create(c.arena, init_node);
} else if (init_node.tag() == .string_literal and qualTypeIsCharStar(qual_type)) {
const dst_type_node = try transQualType(c, scope, qual_type, loc);
init_node = try removeCVQualifiers(c, dst_type_node, init_node);
}

const var_name: []const u8 = if (is_static_local) Scope.Block.StaticInnerName else mangled_name;
Expand Down Expand Up @@ -2522,9 +2566,19 @@ fn transInitListExprRecord(
raw_name = try mem.dupe(c.arena, u8, name);
}

var init_expr = try transExpr(c, scope, elem_expr, .used);
const field_qt = field_decl.getType();
if (init_expr.tag() == .string_literal and qualTypeIsCharStar(field_qt)) {
if (scope.id == .root) {
init_expr = try stringLiteralToCharStar(c, scope, init_expr);
} else {
const dst_type_node = try transQualType(c, scope, field_qt, loc);
init_expr = try removeCVQualifiers(c, dst_type_node, init_expr);
}
}
try field_inits.append(.{
.name = raw_name,
.value = try transExpr(c, scope, elem_expr, .used),
.value = init_expr,
});
}
if (ty_node.castTag(.identifier)) |ident_node| {
Expand Down Expand Up @@ -3459,6 +3513,10 @@ fn transCallExpr(c: *Context, scope: *Scope, stmt: *const clang.CallExpr, result
const param_qt = fn_proto.getParamType(@intCast(c_uint, i));
if (isBoolRes(arg) and cIsNativeInt(param_qt)) {
arg = try Tag.bool_to_int.create(c.arena, arg);
} else if (arg.tag() == .string_literal and qualTypeIsCharStar(param_qt)) {
const loc = @ptrCast(*const clang.Stmt, stmt).getBeginLoc();
const dst_type_node = try transQualType(c, scope, param_qt, loc);
arg = try removeCVQualifiers(c, dst_type_node, arg);
}
}
},
Expand Down Expand Up @@ -3835,6 +3893,12 @@ fn transCreateCompoundAssign(
return block_scope.complete(c);
}

// Casting away const or volatile requires us to use @intToPtr
fn removeCVQualifiers(c: *Context, dst_type_node: Node, expr: Node) Error!Node {
const ptr_to_int = try Tag.ptr_to_int.create(c.arena, expr);
return Tag.int_to_ptr.create(c.arena, .{ .lhs = dst_type_node, .rhs = ptr_to_int });
}

fn transCPtrCast(
c: *Context,
scope: *Scope,
Expand All @@ -3854,10 +3918,7 @@ fn transCPtrCast(
(src_child_type.isVolatileQualified() and
!child_type.isVolatileQualified())))
{
// Casting away const or volatile requires us to use @intToPtr
const ptr_to_int = try Tag.ptr_to_int.create(c.arena, expr);
const int_to_ptr = try Tag.int_to_ptr.create(c.arena, .{ .lhs = dst_type_node, .rhs = ptr_to_int });
return int_to_ptr;
return removeCVQualifiers(c, dst_type_node, expr);
} else {
// Implicit downcasting from higher to lower alignment values is forbidden,
// use @alignCast to side-step this problem
Expand Down Expand Up @@ -4217,6 +4278,26 @@ fn typeIsOpaque(c: *Context, ty: *const clang.Type, loc: clang.SourceLocation) b
}
}

/// plain `char *` (not const; not explicitly signed or unsigned)
fn qualTypeIsCharStar(qt: clang.QualType) bool {
if (qualTypeIsPtr(qt)) {
const child_qt = qualTypeCanon(qt).getPointeeType();
return cIsUnqualifiedChar(child_qt) and !child_qt.isConstQualified();
}
return false;
}

/// C `char` without explicit signed or unsigned qualifier
fn cIsUnqualifiedChar(qt: clang.QualType) bool {
const c_type = qualTypeCanon(qt);
if (c_type.getTypeClass() != .Builtin) return false;
const builtin_ty = @ptrCast(*const clang.BuiltinType, c_type);
return switch (builtin_ty.getKind()) {
.Char_S, .Char_U => true,
else => false,
};
}

fn cIsInteger(qt: clang.QualType) bool {
return cIsSignedInteger(qt) or cIsUnsignedInteger(qt);
}
Expand Down
15 changes: 10 additions & 5 deletions src/translate_c/ast.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -558,9 +558,10 @@ pub const Payload = struct {
pub const Record = struct {
base: Payload,
data: struct {
is_packed: bool,
layout: enum { @"packed", @"extern", none },
fields: []Field,
functions: []Node,
variables: []Node,
},

pub const Field = struct {
Expand Down Expand Up @@ -1952,9 +1953,9 @@ fn renderNode(c: *Context, node: Node) Allocator.Error!NodeIndex {

fn renderRecord(c: *Context, node: Node) !NodeIndex {
const payload = @fieldParentPtr(Payload.Record, "base", node.ptr_otherwise).data;
if (payload.is_packed)
if (payload.layout == .@"packed")
_ = try c.addToken(.keyword_packed, "packed")
else
else if (payload.layout == .@"extern")
_ = try c.addToken(.keyword_extern, "extern");
const kind_tok = if (node.tag() == .@"struct")
try c.addToken(.keyword_struct, "struct")
Expand All @@ -1963,8 +1964,9 @@ fn renderRecord(c: *Context, node: Node) !NodeIndex {

_ = try c.addToken(.l_brace, "{");

const num_vars = payload.variables.len;
const num_funcs = payload.functions.len;
const total_members = payload.fields.len + num_funcs;
const total_members = payload.fields.len + num_vars + num_funcs;
const members = try c.gpa.alloc(NodeIndex, std.math.max(total_members, 2));
defer c.gpa.free(members);
members[0] = 0;
Expand Down Expand Up @@ -2006,8 +2008,11 @@ fn renderRecord(c: *Context, node: Node) !NodeIndex {
});
_ = try c.addToken(.comma, ",");
}
for (payload.variables) |variable, i| {
members[payload.fields.len + i] = try renderNode(c, variable);
}
for (payload.functions) |function, i| {
members[payload.fields.len + i] = try renderNode(c, function);
members[payload.fields.len + num_vars + i] = try renderNode(c, function);
}
_ = try c.addToken(.r_brace, "}");

Expand Down
18 changes: 18 additions & 0 deletions test/run_translated_c.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1749,4 +1749,22 @@ pub fn addCases(cases: *tests.RunTranslatedCContext) void {
\\ return 0;
\\}
, "");

cases.add("Allow non-const char* string literals. Issue #9126",
\\#include <stdlib.h>
\\int func(char *x) { return x[0]; }
\\struct S { char *member; };
\\struct S global_struct = { .member = "global" };
\\char *g = "global";
\\int main(void) {
\\ if (g[0] != 'g') abort();
\\ if (global_struct.member[0] != 'g') abort();
\\ char *string = "hello";
\\ if (string[0] != 'h') abort();
\\ struct S s = {.member = "hello"};
\\ if (s.member[0] != 'h') abort();
\\ if (func("foo") != 'f') abort();
\\ return 0;
\\}
, "");
}

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