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

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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
This commit is contained in:
Peter Klausler 2022-11-04 16:39:52 -07:00
parent 0041382198
commit 8a1f12c6fb
4 changed files with 276 additions and 3 deletions
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2
flang/docs/Extensions.md
View File

@ -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

13
flang/lib/Parser/prescan.cpp
View File

@ -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();

2
flang/lib/Parser/prescan.h
View File

@ -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

262
flang/test/Parser/excessive-continuations.f90 Normal file
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@ -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