Add a warning, flags and pragmas to limit the number of pre-processor tokens in a translation unit
See
https://docs.google.com/document/d/1xMkTZMKx9llnMPgso0jrx3ankI4cv60xeZ0y4ksf4wc/preview
for background discussion.
This adds a warning, flags and pragmas to limit the number of
pre-processor tokens either at a certain point in a translation unit, or
overall.
The idea is that this would allow projects to limit the size of certain
widely included headers, or for translation units overall, as a way to
insert backstops for header bloat and prevent compile-time regressions.
Differential revision: https://reviews.llvm.org/D72703
diff --git a/clang/lib/Parse/ParsePragma.cpp b/clang/lib/Parse/ParsePragma.cpp
index df411e1..ec50847 100644
--- a/clang/lib/Parse/ParsePragma.cpp
+++ b/clang/lib/Parse/ParsePragma.cpp
@@ -262,6 +262,18 @@
ParsedAttributes AttributesForPragmaAttribute;
};
+struct PragmaMaxTokensHereHandler : public PragmaHandler {
+ PragmaMaxTokensHereHandler() : PragmaHandler("max_tokens_here") {}
+ void HandlePragma(Preprocessor &PP, PragmaIntroducer Introducer,
+ Token &FirstToken) override;
+};
+
+struct PragmaMaxTokensTotalHandler : public PragmaHandler {
+ PragmaMaxTokensTotalHandler() : PragmaHandler("max_tokens_total") {}
+ void HandlePragma(Preprocessor &PP, PragmaIntroducer Introducer,
+ Token &FirstToken) override;
+};
+
} // end namespace
void Parser::initializePragmaHandlers() {
@@ -382,6 +394,12 @@
AttributePragmaHandler =
std::make_unique<PragmaAttributeHandler>(AttrFactory);
PP.AddPragmaHandler("clang", AttributePragmaHandler.get());
+
+ MaxTokensHerePragmaHandler = std::make_unique<PragmaMaxTokensHereHandler>();
+ PP.AddPragmaHandler("clang", MaxTokensHerePragmaHandler.get());
+
+ MaxTokensTotalPragmaHandler = std::make_unique<PragmaMaxTokensTotalHandler>();
+ PP.AddPragmaHandler("clang", MaxTokensTotalPragmaHandler.get());
}
void Parser::resetPragmaHandlers() {
@@ -487,6 +505,12 @@
PP.RemovePragmaHandler("clang", AttributePragmaHandler.get());
AttributePragmaHandler.reset();
+
+ PP.RemovePragmaHandler("clang", MaxTokensHerePragmaHandler.get());
+ MaxTokensHerePragmaHandler.reset();
+
+ PP.RemovePragmaHandler("clang", MaxTokensTotalPragmaHandler.get());
+ MaxTokensTotalPragmaHandler.reset();
}
/// Handle the annotation token produced for #pragma unused(...)
@@ -3279,3 +3303,64 @@
PP.EnterTokenStream(std::move(TokenArray), 1,
/*DisableMacroExpansion=*/false, /*IsReinject=*/false);
}
+
+// Handle '#pragma clang max_tokens 12345'.
+void PragmaMaxTokensHereHandler::HandlePragma(Preprocessor &PP,
+ PragmaIntroducer Introducer,
+ Token &Tok) {
+ PP.Lex(Tok);
+ if (Tok.is(tok::eod)) {
+ PP.Diag(Tok.getLocation(), diag::err_pragma_missing_argument)
+ << "clang max_tokens_here" << /*Expected=*/true << "integer";
+ return;
+ }
+
+ SourceLocation Loc = Tok.getLocation();
+ uint64_t MaxTokens;
+ if (Tok.isNot(tok::numeric_constant) ||
+ !PP.parseSimpleIntegerLiteral(Tok, MaxTokens)) {
+ PP.Diag(Tok.getLocation(), diag::err_pragma_expected_integer)
+ << "clang max_tokens_here";
+ return;
+ }
+
+ if (Tok.isNot(tok::eod)) {
+ PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
+ << "clang max_tokens_here";
+ return;
+ }
+
+ if (PP.getTokenCount() > MaxTokens) {
+ PP.Diag(Loc, diag::warn_max_tokens)
+ << PP.getTokenCount() << (unsigned)MaxTokens;
+ }
+}
+
+// Handle '#pragma clang max_file_tokens 12345'.
+void PragmaMaxTokensTotalHandler::HandlePragma(Preprocessor &PP,
+ PragmaIntroducer Introducer,
+ Token &Tok) {
+ PP.Lex(Tok);
+ if (Tok.is(tok::eod)) {
+ PP.Diag(Tok.getLocation(), diag::err_pragma_missing_argument)
+ << "clang max_tokens_total" << /*Expected=*/true << "integer";
+ return;
+ }
+
+ SourceLocation Loc = Tok.getLocation();
+ uint64_t MaxTokens;
+ if (Tok.isNot(tok::numeric_constant) ||
+ !PP.parseSimpleIntegerLiteral(Tok, MaxTokens)) {
+ PP.Diag(Tok.getLocation(), diag::err_pragma_expected_integer)
+ << "clang max_tokens_total";
+ return;
+ }
+
+ if (Tok.isNot(tok::eod)) {
+ PP.Diag(Tok.getLocation(), diag::warn_pragma_extra_tokens_at_eol)
+ << "clang max_tokens_total";
+ return;
+ }
+
+ PP.overrideMaxTokens(MaxTokens, Loc);
+}