[flang] Warn about more continuation lines than the standard permits

f18 doesn't have any limit on continuation lines in fixed or free form
source (other than available memory), but the standard does.  Emit
a portability warning when it is exceeded.

Differential Revision: https://reviews.llvm.org/D139055

diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md
index ed0229d..039b1f9 100644 (file)
--- a/flang/docs/Extensions.md
+++ b/flang/docs/Extensions.md
@@ -240,6 +240,8 @@ end
 * The legacy extension intrinsic functions `IZEXT` and `JZEXT`
   are supported; `ZEXT` has different behavior with various older
   compilers, so it is not supported.
+* f18 doesn't impose a limit on the number of continuation lines
+  allowed for a single statement.
 
 ### Extensions supported when enabled by options
 

diff --git a/flang/lib/Parser/prescan.cpp b/flang/lib/Parser/prescan.cpp
index 17fc090..ae8decf 100644 (file)
--- a/flang/lib/Parser/prescan.cpp
+++ b/flang/lib/Parser/prescan.cpp
@@ -89,7 +89,8 @@ void Prescanner::Prescan(ProvenanceRange range) {
 
 void Prescanner::Statement() {
   TokenSequence tokens;
-  LineClassification line{ClassifyLine(nextLine_)};
+  const char *statementStart{nextLine_};
+  LineClassification line{ClassifyLine(statementStart)};
   switch (line.kind) {
   case LineClassification::Kind::Comment:
     nextLine_ += line.payloadOffset; // advance to '!' or newline
@@ -164,6 +165,11 @@ void Prescanner::Statement() {
 
   while (NextToken(tokens)) {
   }
+  if (continuationLines_ > 255) {
+    Say(GetProvenance(statementStart),
+        "%d continuation lines is more than the Fortran standard allows"_port_en_US,
+        continuationLines_);
+  }
 
   Provenance newlineProvenance{GetCurrentProvenance()};
   if (std::optional<TokenSequence> preprocessed{
@@ -299,7 +305,7 @@ void Prescanner::LabelField(TokenSequence &token) {
   token.CloseToken();
   SkipToNextSignificantCharacter();
   if (IsDecimalDigit(*at_)) {
-    Say(GetProvenance(at_),
+    Say(GetCurrentProvenance(),
         "Label digit is not in fixed-form label field"_port_en_US);
   }
 }
@@ -406,6 +412,7 @@ void Prescanner::SkipToNextSignificantCharacter() {
       mightNeedSpace = *at_ == '\n';
     }
     for (; Continuation(mightNeedSpace); mightNeedSpace = false) {
+      ++continuationLines_;
       if (MustSkipToEndOfLine()) {
         SkipToEndOfLine();
       }
@@ -493,7 +500,7 @@ bool Prescanner::NextToken(TokenSequence &tokens) {
       // Recognize and skip over classic C style /*comments*/ when
       // outside a character literal.
       if (features_.ShouldWarn(LanguageFeature::ClassicCComments)) {
-        Say(GetProvenance(at_),
+        Say(GetCurrentProvenance(),
             "nonstandard usage: C-style comment"_port_en_US);
       }
       SkipCComments();

diff --git a/flang/lib/Parser/prescan.h b/flang/lib/Parser/prescan.h
index 4d002ad..ad8b90b 100644 (file)
--- a/flang/lib/Parser/prescan.h
+++ b/flang/lib/Parser/prescan.h
@@ -109,6 +109,7 @@ private:
     slashInCurrentStatement_ = false;
     preventHollerith_ = false;
     delimiterNesting_ = 0;
+    continuationLines_ = 0;
   }
 
   Provenance GetProvenance(const char *sourceChar) const {
@@ -195,6 +196,7 @@ private:
   Encoding encoding_{Encoding::UTF_8};
   int delimiterNesting_{0};
   int prescannerNesting_{0};
+  int continuationLines_{0};
 
   Provenance startProvenance_;
   const char *start_{nullptr}; // beginning of current source file content

diff --git a/flang/test/Parser/excessive-continuations.f90 b/flang/test/Parser/excessive-continuations.f90
new file mode 100644 (file)
index 0000000..e5855cf
--- /dev/null
+++ b/flang/test/Parser/excessive-continuations.f90
@@ -0,0 +1,262 @@
+! RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
+! CHECK: portability: 256 continuation lines is more than the Fortran standard allows
+! CHECK: LOGICAL, PARAMETER :: c255 = .true._4
+program test
+  logical, parameter :: c255 = 255 == len("&
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+end