[flang-commits] [flang] 1746c8e - [flang] Fixed crash on forward referenced `len` parameter

[Pete Steinfeld via flang-commits]

Author: Pete Steinfeld
Date: 2020-06-04T13:12:11-07:00
New Revision: 1746c8ed2660c83895c79de94453f44f8e729a94

URL: https://github.com/llvm/llvm-project/commit/1746c8ed2660c83895c79de94453f44f8e729a94
DIFF: https://github.com/llvm/llvm-project/commit/1746c8ed2660c83895c79de94453f44f8e729a94.diff

LOG: [flang] Fixed crash on forward referenced `len` parameter

Summary:
Using a forward reference to define a `len` parameter causes a crash.
The underlying cause was that a previously declared type had an
erroneous expression for its `LEN` param value.  When this expression
was referenced to evaluate a subsequent expression, bad things happened.
I fixed this by putting in code to detect this case.

Reviewers: tskeith, klausler, DavidTruby

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80593

Added: 
    

Modified: 
    flang/lib/Evaluate/variable.cpp
    flang/test/Semantics/resolve91.f90

Removed: 
    


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diff  --git a/flang/lib/Evaluate/variable.cpp b/flang/lib/Evaluate/variable.cpp
index c7b261d27e9a..3a6cf560384c 100644
--- a/flang/lib/Evaluate/variable.cpp
+++ b/flang/lib/Evaluate/variable.cpp
@@ -257,8 +257,14 @@ DescriptorInquiry::DescriptorInquiry(NamedEntity &&base, Field field, int dim)
 static std::optional<Expr<SubscriptInteger>> SymbolLEN(const Symbol &sym) {
   if (auto dyType{DynamicType::From(sym)}) {
     if (const semantics::ParamValue * len{dyType->charLength()}) {
-      if (auto intExpr{len->GetExplicit()}) {
-        return ConvertToType<SubscriptInteger>(*std::move(intExpr));
+      if (len->isExplicit()) {
+        if (auto intExpr{len->GetExplicit()}) {
+          return ConvertToType<SubscriptInteger>(*std::move(intExpr));
+        } else {
+          // There was an error constructing this symbol's type.  It should
+          // have a length expression, but we couldn't retrieve it
+          return std::nullopt;
+        }
       } else {
         return Expr<SubscriptInteger>{
             DescriptorInquiry{NamedEntity{sym}, DescriptorInquiry::Field::Len}};

diff  --git a/flang/test/Semantics/resolve91.f90 b/flang/test/Semantics/resolve91.f90
index f55ca865cf3c..0a375b873aa4 100644
--- a/flang/test/Semantics/resolve91.f90
+++ b/flang/test/Semantics/resolve91.f90
@@ -44,3 +44,10 @@ module m4
     real, dimension(:), pointer :: realArray => localArray
   end type
 end module m4
+
+module m5
+  !ERROR: Actual argument for 'string=' has bad type 'REAL(4)'
+  character(len=len(a)) :: b
+  !ERROR: The type of 'a' has already been implicitly declared
+  character(len=len(b)) :: a
+end module m5