Commit f6ddfac4 authored by peter klausler's avatar peter klausler
Browse files

[flang] Enforce fixed form rules about END continuation 

From subclause 6.3.3.5: a program unit END statement cannot be
continued in fixed form, and other statements cannot have initial
lines that look like program unit END statements.  I think this
is to avoid violating assumptions that are important to legacy
compilers' statement classification routines.

Differential Revision: https://reviews.llvm.org/D109933
parent 101c3de3

flang/lib/Parser/prescan.cpp

+64 −0
Original line number Diff line number Diff line
@@ -217,6 +217,9 @@ void Prescanner::Statement() { 
    if (line.kind == LineClassification::Kind::CompilerDirective) {

      SourceFormChange(tokens.ToString());

    }

    if (inFixedForm_ && line.kind == LineClassification::Kind::Source) {

      EnforceStupidEndStatementRules(tokens);

    }

    tokens.CheckBadFortranCharacters(messages_).Emit(cooked_);

  }

  if (omitNewline_) {
@@ -288,6 +291,67 @@ void Prescanner::LabelField(TokenSequence &token) { 
  }

}



// 6.3.3.5: A program unit END statement, or any other statement whose

// initial line resembles an END statement, shall not be continued in

// fixed form source.

void Prescanner::EnforceStupidEndStatementRules(const TokenSequence &tokens) {

  CharBlock cBlock{tokens.ToCharBlock()};

  const char *str{cBlock.begin()};

  std::size_t n{cBlock.size()};

  if (n < 3) {

    return;

  }

  std::size_t j{0};

  for (; j < n && (str[j] == ' ' || (str[j] >= '0' && str[j] <= '9')); ++j) {

  }

  if (j + 3 > n || std::memcmp(str + j, "end", 3) != 0) {

    return;

  }

  // It starts with END, possibly after a label.

  auto start{allSources_.GetSourcePosition(tokens.GetCharProvenance(j))};

  auto end{allSources_.GetSourcePosition(tokens.GetCharProvenance(n - 1))};

  if (!start || !end) {

    return;

  }

  if (&start->file == &end->file && start->line == end->line) {

    return; // no continuation

  }

  j += 3;

  static const char *const prefixes[]{"program", "subroutine", "function",

      "blockdata", "module", "submodule", nullptr};

  CharBlock stmt{tokens.ToCharBlock()};

  bool isPrefix{j == n || !IsLegalInIdentifier(str[j])}; // prefix is END

  std::size_t endOfPrefix{j - 1};

  for (const char *const *p{prefixes}; *p; ++p) {

    std::size_t pLen{std::strlen(*p)};

    if (j + pLen <= n && std::memcmp(str + j, *p, pLen) == 0) {

      isPrefix = true; // END thing as prefix

      j += pLen;

      endOfPrefix = j - 1;

      for (; j < n && IsLegalInIdentifier(str[j]); ++j) {

      }

      break;

    }

  }

  if (isPrefix) {

    auto range{tokens.GetTokenProvenanceRange(1)};

    if (j == n) { // END or END thing [name]

      Say(range,

          "Program unit END statement may not be continued in fixed form source"_err_en_US);

    } else {

      auto endOfPrefixPos{

          allSources_.GetSourcePosition(tokens.GetCharProvenance(endOfPrefix))};

      auto next{allSources_.GetSourcePosition(tokens.GetCharProvenance(j))};

      if (endOfPrefixPos && next && &endOfPrefixPos->file == &start->file &&

          endOfPrefixPos->line == start->line &&

          (&next->file != &start->file || next->line != start->line)) {

        Say(range,

            "Initial line of continued statement must not appear to be a program unit END in fixed form source"_err_en_US);

      }

    }

  }

}



void Prescanner::SkipToEndOfLine() {

  while (*at_ != '\n') {

    ++at_, ++column_;

flang/lib/Parser/prescan.h

+1 −0
Original line number Diff line number Diff line
@@ -150,6 +150,7 @@ private: 
  }



  void LabelField(TokenSequence &);

  void EnforceStupidEndStatementRules(const TokenSequence &);

  void SkipToEndOfLine();

  bool MustSkipToEndOfLine() const;

  void NextChar();

flang/lib/Parser/token-sequence.cpp

+6 −2
Original line number Diff line number Diff line
@@ -286,10 +286,14 @@ llvm::raw_ostream &TokenSequence::Dump(llvm::raw_ostream &o) const { 
  return o;

}



Provenance TokenSequence::GetCharProvenance(std::size_t offset) const {

  ProvenanceRange range{provenances_.Map(offset)};

  return range.start();

}



Provenance TokenSequence::GetTokenProvenance(

    std::size_t token, std::size_t offset) const {

  ProvenanceRange range{provenances_.Map(start_[token] + offset)};

  return range.start();

  return GetCharProvenance(start_[token] + offset);

}



ProvenanceRange TokenSequence::GetTokenProvenanceRange(

flang/lib/Parser/token-sequence.h

+1 −0
Original line number Diff line number Diff line
@@ -102,6 +102,7 @@ public: 
  void Put(const std::string &, Provenance);

  void Put(llvm::raw_string_ostream &, Provenance);



  Provenance GetCharProvenance(std::size_t) const;

  Provenance GetTokenProvenance(

      std::size_t token, std::size_t offset = 0) const;

  ProvenanceRange GetTokenProvenanceRange(

flang/test/Parser/end.f

0 → 100644
+29 −0
Original line number Diff line number Diff line 
! RUN: not %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck %s

! CHECK: end.f:3:7: error: Program unit END statement may not be continued in fixed form source

      e

     + nd

! CHECK: end.f:6:7: error: Program unit END statement may not be continued in fixed form source

      end prog

     +        ram

! CHECK: end.f:9:7: error: Program unit END statement may not be continued in fixed form source

      end

     +       program

! CHECK: end.f:12:7: error: Program unit END statement may not be continued in fixed form source

      end

     +       program

     1                main

! CHECK: end.f:16:7: error: Program unit END statement may not be continued in fixed form source

      end program

     1            main

! CHECK: end.f:19:7: error: Initial line of continued statement must not appear to be a program unit END in fixed form source

      end

     +    = end + 1

! CHECK: end.f:22:7: error: Initial line of continued statement must not appear to be a program unit END in fixed form source

      end module

     +    = end module + 1

! CHECK-NOT: end.f:25:7: error: Initial line of continued statement must not appear to be a program unit END in fixed form source

      end =

     +      end + 1

! CHECK-NOT: end.f:28:7: error: Initial line of continued statement must not appear to be a program unit END in fixed form source

      end block data (

     +      1) = 666