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translate-c: Ensure assignments are within a block when necessary

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Ensures that if an assignment statement is the sole statement within a
C if statement, for loop, do loop, or do while loop, then when translated
it resides within a block, even though it does not in the original C.

Fixes the following invalid translation:

`if (1) if (1) 2;` -> `if (true) if (true) _ = @as(c_int, 2);`

To this:
```zig
    if (true) if (true) {
        _ = @as(c_int, 2);
    };
```

Fixes #8159
This commit is contained in:
Evan Haas 2021-03-18 23:13:59 -07:00 committed by Veikka Tuominen
parent 187af14599
commit dce612ac2b
3 changed files with 62 additions and 9 deletions
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41
src/translate_c.zig
View File

@ -1063,6 +1063,7 @@ fn transStmt(
const gen_sel = @ptrCast(*const clang.GenericSelectionExpr, stmt);
return transExpr(c, scope, gen_sel.getResultExpr(), result_used);
},
// When adding new cases here, see comment for maybeBlockify()
else => {
return fail(c, error.UnsupportedTranslation, stmt.getBeginLoc(), "TODO implement translation of stmt class {s}", .{@tagName(sc)});
},
@ -2242,6 +2243,35 @@ fn transImplicitValueInitExpr(
return transZeroInitExpr(c, scope, source_loc, ty);
}
/// If a statement can possibly translate to a Zig assignment (either directly because it's
/// an assignment in C or indirectly via result assignment to `_`) AND it's the sole statement
/// in the body of an if statement or loop, then we need to put the statement into its own block.
/// The `else` case here corresponds to statements that could result in an assignment. If a statement
/// class never needs a block, add its enum to the top prong.
fn maybeBlockify(c: *Context, scope: *Scope, stmt: *const clang.Stmt) TransError!Node {
switch (stmt.getStmtClass()) {
.BreakStmtClass,
.CompoundStmtClass,
.ContinueStmtClass,
.DeclRefExprClass,
.DeclStmtClass,
.DoStmtClass,
.ForStmtClass,
.IfStmtClass,
.ReturnStmtClass,
.NullStmtClass,
.WhileStmtClass,
=> return transStmt(c, scope, stmt, .unused),
else => {
var block_scope = try Scope.Block.init(c, scope, false);
defer block_scope.deinit();
const result = try transStmt(c, &block_scope.base, stmt, .unused);
try block_scope.statements.append(result);
return block_scope.complete(c);
},
}
}
fn transIfStmt(
c: *Context,
scope: *Scope,
@ -2259,9 +2289,10 @@ fn transIfStmt(
const cond_expr = @ptrCast(*const clang.Expr, stmt.getCond());
const cond = try transBoolExpr(c, &cond_scope.base, cond_expr, .used);
const then_body = try transStmt(c, scope, stmt.getThen(), .unused);
const then_body = try maybeBlockify(c, scope, stmt.getThen());
const else_body = if (stmt.getElse()) |expr|
try transStmt(c, scope, expr, .unused)
try maybeBlockify(c, scope, expr)
else
null;
return Tag.@"if".create(c.arena, .{ .cond = cond, .then = then_body, .@"else" = else_body });
@ -2286,7 +2317,7 @@ fn transWhileLoop(
.parent = scope,
.id = .loop,
};
const body = try transStmt(c, &loop_scope, stmt.getBody(), .unused);
const body = try maybeBlockify(c, &loop_scope, stmt.getBody());
return Tag.@"while".create(c.arena, .{ .cond = cond, .body = body, .cont_expr = null });
}
@ -2312,7 +2343,7 @@ fn transDoWhileLoop(
const if_not_break = switch (cond.tag()) {
.false_literal => return transStmt(c, scope, stmt.getBody(), .unused),
.true_literal => {
const body_node = try transStmt(c, scope, stmt.getBody(), .unused);
const body_node = try maybeBlockify(c, scope, stmt.getBody());
return Tag.while_true.create(c.arena, body_node);
},
else => try Tag.if_not_break.create(c.arena, cond),
@ -2388,7 +2419,7 @@ fn transForLoop(
else
null;
const body = try transStmt(c, &loop_scope, stmt.getBody(), .unused);
const body = try maybeBlockify(c, &loop_scope, stmt.getBody());
const while_node = try Tag.@"while".create(c.arena, .{ .cond = cond, .body = body, .cont_expr = cont_expr });
if (block_scope) |*bs| {
try bs.statements.append(while_node);

14
test/run_translated_c.zig
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@ -1244,4 +1244,18 @@ pub fn addCases(cases: *tests.RunTranslatedCContext) void {
\\ return 0;
\\}
, "");
cases.add("convert single-statement bodies into blocks for if/else/for/while. issue #8159",
\\#include <stdlib.h>
\\int foo() { return 1; }
\\int main(void) {
\\ int i = 0;
\\ if (i == 0) if (i == 0) if (i != 0) i = 1;
\\ if (i != 0) i = 1; else if (i == 0) if (i == 0) i += 1;
\\ for (; i < 10;) for (; i < 10;) i++;
\\ while (i == 100) while (i == 100) foo();
\\ if (0) do do "string"; while(1); while(1);
\\ return 0;
\\}
, "");
}

16
test/translate_c.zig
View File

@ -1934,7 +1934,9 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
, &[_][]const u8{
\\pub export fn foo() c_int {
\\ var a: c_int = 5;
\\ while (true) a = 2;
\\ while (true) {
\\ a = 2;
\\ }
\\ while (true) {
\\ var a_1: c_int = 4;
\\ a_1 = 9;
@ -1947,7 +1949,9 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
\\ var a_1: c_int = 2;
\\ a_1 = 12;
\\ }
\\ while (true) a = 7;
\\ while (true) {
\\ a = 7;
\\ }
\\ return 0;
\\}
});
@ -2008,7 +2012,9 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
\\}
, &[_][]const u8{
\\pub export fn bar() c_int {
\\ if ((if (true) @as(c_int, 5) else if (true) @as(c_int, 4) else @as(c_int, 6)) != 0) _ = @as(c_int, 2);
\\ if ((if (true) @as(c_int, 5) else if (true) @as(c_int, 4) else @as(c_int, 6)) != 0) {
\\ _ = @as(c_int, 2);
\\ }
\\ return if (true) @as(c_int, 5) else if (true) @as(c_int, 4) else @as(c_int, 6);
\\}
});
@ -2389,7 +2395,9 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
\\pub const yes = [*c]u8;
\\pub export fn foo() void {
\\ var a: yes = undefined;
\\ if (a != null) _ = @as(c_int, 2);
\\ if (a != null) {
\\ _ = @as(c_int, 2);
\\ }
\\}
});