[flang] Catch mismatched parentheses in prescanner
Source lines with mismatched parentheses are hard cases for error
recovery in parsing, and the best error message (viz.,
"here's an unmatched parenthesis") can be emitted from the
prescanner.
Differential Revision: https://reviews.llvm.org/D111254#3046173
GitOrigin-RevId: 094b380c210ac508a1ad5a7c47a760773b0cc6ea
diff --git a/lib/Parser/prescan.cpp b/lib/Parser/prescan.cpp
index 0531ffd..7d7ee36 100644
--- a/lib/Parser/prescan.cpp
+++ b/lib/Parser/prescan.cpp
@@ -169,7 +169,7 @@
preprocessed->CloseToken();
const char *ppd{preprocessed->ToCharBlock().begin()};
LineClassification ppl{ClassifyLine(ppd)};
- preprocessed->RemoveLastToken(); // remove the newline
+ preprocessed->pop_back(); // remove the newline
switch (ppl.kind) {
case LineClassification::Kind::Comment:
break;
@@ -182,8 +182,10 @@
case LineClassification::Kind::PreprocessorDirective:
Say(preprocessed->GetProvenanceRange(),
"Preprocessed line resembles a preprocessor directive"_en_US);
- preprocessed->ToLowerCase().CheckBadFortranCharacters(messages_).Emit(
- cooked_);
+ preprocessed->ToLowerCase()
+ .CheckBadFortranCharacters(messages_)
+ .CheckBadParentheses(messages_)
+ .Emit(cooked_);
break;
case LineClassification::Kind::CompilerDirective:
if (preprocessed->HasRedundantBlanks()) {
@@ -194,6 +196,7 @@
SourceFormChange(preprocessed->ToString());
preprocessed->ClipComment(true /* skip first ! */)
.CheckBadFortranCharacters(messages_)
+ .CheckBadParentheses(messages_)
.Emit(cooked_);
break;
case LineClassification::Kind::Source:
@@ -209,6 +212,7 @@
preprocessed->ToLowerCase()
.ClipComment()
.CheckBadFortranCharacters(messages_)
+ .CheckBadParentheses(messages_)
.Emit(cooked_);
break;
}
@@ -220,7 +224,9 @@
if (inFixedForm_ && line.kind == LineClassification::Kind::Source) {
EnforceStupidEndStatementRules(tokens);
}
- tokens.CheckBadFortranCharacters(messages_).Emit(cooked_);
+ tokens.CheckBadFortranCharacters(messages_)
+ .CheckBadParentheses(messages_)
+ .Emit(cooked_);
}
if (omitNewline_) {
omitNewline_ = false;
@@ -255,6 +261,7 @@
void Prescanner::LabelField(TokenSequence &token) {
const char *bad{nullptr};
int outCol{1};
+ const char *start{at_};
for (; *at_ != '\n' && column_ <= 6; ++at_) {
if (*at_ == '\t') {
++at_;
@@ -271,17 +278,19 @@
}
++column_;
}
+ if (bad && !preprocessor_.IsNameDefined(token.CurrentOpenToken())) {
+ Say(GetProvenance(bad),
+ "Character in fixed-form label field must be a digit"_en_US);
+ token.clear();
+ at_ = start;
+ return;
+ }
if (outCol == 1) { // empty label field
// Emit a space so that, if the line is rescanned after preprocessing,
// a leading 'C' or 'D' won't be left-justified and then accidentally
// misinterpreted as a comment card.
EmitChar(token, ' ');
++outCol;
- } else {
- if (bad && !preprocessor_.IsNameDefined(token.CurrentOpenToken())) {
- Say(GetProvenance(bad),
- "Character in fixed-form label field must be a digit"_en_US);
- }
}
token.CloseToken();
SkipToNextSignificantCharacter();
diff --git a/lib/Parser/token-sequence.cpp b/lib/Parser/token-sequence.cpp
index 3ed9d05..55217a9 100644
--- a/lib/Parser/token-sequence.cpp
+++ b/lib/Parser/token-sequence.cpp
@@ -27,6 +27,8 @@
}
void TokenSequence::pop_back() {
+ CHECK(!start_.empty());
+ CHECK(nextStart_ > start_.back());
std::size_t bytes{nextStart_ - start_.back()};
nextStart_ = start_.back();
start_.pop_back();
@@ -82,16 +84,6 @@
return false;
}
-void TokenSequence::RemoveLastToken() {
- CHECK(!start_.empty());
- CHECK(nextStart_ > start_.back());
- std::size_t bytes{nextStart_ - start_.back()};
- nextStart_ = start_.back();
- start_.pop_back();
- char_.erase(char_.begin() + nextStart_, char_.end());
- provenances_.RemoveLastBytes(bytes);
-}
-
void TokenSequence::Put(const TokenSequence &that) {
if (nextStart_ < char_.size()) {
start_.push_back(nextStart_);
@@ -338,4 +330,41 @@
}
return *this;
}
+
+const TokenSequence &TokenSequence::CheckBadParentheses(
+ Messages &messages) const {
+ // First, a quick pass with no allocation for the common case
+ int nesting{0};
+ std::size_t tokens{SizeInTokens()};
+ for (std::size_t j{0}; j < tokens; ++j) {
+ CharBlock token{TokenAt(j)};
+ char ch{token.FirstNonBlank()};
+ if (ch == '(') {
+ ++nesting;
+ } else if (ch == ')') {
+ --nesting;
+ }
+ }
+ if (nesting != 0) {
+ // There's an error; diagnose it
+ std::vector<std::size_t> stack;
+ for (std::size_t j{0}; j < tokens; ++j) {
+ CharBlock token{TokenAt(j)};
+ char ch{token.FirstNonBlank()};
+ if (ch == '(') {
+ stack.push_back(j);
+ } else if (ch == ')') {
+ if (stack.empty()) {
+ messages.Say(GetTokenProvenanceRange(j), "Unmatched ')'"_err_en_US);
+ return *this;
+ }
+ stack.pop_back();
+ }
+ }
+ CHECK(!stack.empty());
+ messages.Say(
+ GetTokenProvenanceRange(stack.back()), "Unmatched '('"_err_en_US);
+ }
+ return *this;
+}
} // namespace Fortran::parser
diff --git a/lib/Parser/token-sequence.h b/lib/Parser/token-sequence.h
index 6da6229..c039126 100644
--- a/lib/Parser/token-sequence.h
+++ b/lib/Parser/token-sequence.h
@@ -92,8 +92,6 @@
start_.pop_back();
}
- void RemoveLastToken();
-
void Put(const TokenSequence &);
void Put(const TokenSequence &, ProvenanceRange);
void Put(const TokenSequence &, std::size_t at, std::size_t tokens = 1);
@@ -119,6 +117,7 @@
TokenSequence &RemoveRedundantBlanks(std::size_t firstChar = 0);
TokenSequence &ClipComment(bool skipFirst = false);
const TokenSequence &CheckBadFortranCharacters(Messages &) const;
+ const TokenSequence &CheckBadParentheses(Messages &) const;
void Emit(CookedSource &) const;
llvm::raw_ostream &Dump(llvm::raw_ostream &) const;
diff --git a/test/Parser/unmatched-parens.f90 b/test/Parser/unmatched-parens.f90
new file mode 100644
index 0000000..c0a3e84
--- /dev/null
+++ b/test/Parser/unmatched-parens.f90
@@ -0,0 +1,8 @@
+! RUN: not %flang_fc1 -E %s 2>&1 | FileCheck %s
+do i = 1,10
+ ! CHECK: Unmatched '('
+ if (i != 0) then
+ exit
+ endif
+enddo
+end
