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Add support for more complex object-like macros (#6338)

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Uses `clang::Parser::ParseConstantExpression()` to parse the macro
replacement tokens, added as a token stream to the preprocessor. This
extends the support from simple object-like macros with a single
replacement token, to multiple tokens like unary operators, binary
operators, casting, nested macros etc.
The support is still limited to macros that are evaluated to an integer
constant. More types to be added as a follow-up.

Part of #6303
This commit is contained in:
Ivana Ivanovska
2025-11-12 17:06:39 +00:00
committed by GitHub
parent 8ba0274e81
commit b68b6ae1e7
4 changed files with 365 additions and 51 deletions
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toolchain/check/cpp/macros.cpp
+40 -14
View File
@@ -5,6 +5,8 @@
#include "toolchain/check/cpp/macros.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Expr.h"
#include "clang/Parse/Parser.h"
#include "clang/Sema/Sema.h"
namespace Carbon::Check {
@@ -14,24 +16,41 @@ auto TryEvaluateMacroToConstant(Context& context, SemIR::LocId loc_id,
clang::MacroInfo* macro_info) -> clang::Expr* {
auto name_str_opt = context.names().GetAsStringIfIdentifier(name_id);
CARBON_CHECK(macro_info, "macro info missing");
if (macro_info->getNumTokens() != 1) {
context.TODO(loc_id,
llvm::formatv("Unsupported: macro with {0} replacement tokens",
macro_info->getNumTokens()));
return nullptr;
}
const clang::Token& tok = macro_info->getReplacementToken(0);
if (!tok.is(clang::tok::numeric_constant)) {
context.TODO(loc_id,
"Unsupported: macro replacement token kind: " +
std::string(clang::tok::getTokenName(tok.getKind())));
if (macro_info->getNumTokens() == 0) {
context.TODO(loc_id, "Unsupported: macro with 0 replacement tokens");
return nullptr;
}
clang::Sema& sema = context.clang_sema();
clang::ExprResult result = sema.ActOnNumericConstant(tok);
clang::Preprocessor& preprocessor = sema.getPreprocessor();
clang::Parser parser(preprocessor, sema, false);
llvm::SmallVector<clang::Token> tokens(macro_info->tokens().begin(),
macro_info->tokens().end());
clang::Token current_token = parser.getCurToken();
// Add eof token
clang::Token eof;
eof.startToken();
eof.setKind(clang::tok::eof);
eof.setLocation(current_token.getEndLoc());
tokens.push_back(eof);
tokens.push_back(current_token);
preprocessor.EnterTokenStream(tokens, false, false);
parser.ConsumeAnyToken(true);
clang::ExprResult result = parser.ParseConstantExpression();
clang::Expr* result_expr = result.get();
if (!result_expr || result.isInvalid()) {
bool success =
!result.isInvalid() && parser.getCurToken().is(clang::tok::eof);
if (!success) {
parser.SkipUntil(clang::tok::eof);
CARBON_DIAGNOSTIC(
InCppMacroEvaluation, Error,
"failed to evaluate macro Cpp.{0} to a valid constant expression",
@@ -40,7 +59,14 @@ auto TryEvaluateMacroToConstant(Context& context, SemIR::LocId loc_id,
return nullptr;
}
return result_expr;
clang::Expr::EvalResult evaluated_result;
if (!result_expr->EvaluateAsInt(evaluated_result, sema.getASTContext())) {
context.TODO(loc_id, "non-integer constant expression in macro.");
return nullptr;
}
return clang::IntegerLiteral::Create(
sema.getASTContext(), evaluated_result.Val.getInt(),
result_expr->getType(), result_expr->getExprLoc());
}
} // namespace Carbon::Check