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[flang] Fix bad dereference of NULLIFY pointer object 

When we have a subprogram that has been determined to contain errors, we do not
perform name resolution on its execution part.  In this case, if the subprogram
contains a NULLIFY statement, the parser::Name of a pointer object in a NULLIFY
statement will not have had name resolution performed on it.  Thus, its symbol
will not have been set.  Later, however, we do semantic checking on the NULLIFY
statement.  The code that did this assumed that the parser::Name of the
pointer object was non-null.

I fixed this by just removing the null pointer check for the "symbol" member of
the "parser::Name" of the pointer object when doing semantic checking for
NULLIFY statements.  I also added a test that will make the compiler crash
without this change.

Differential Revision: https://reviews.llvm.org/D98184
This commit is contained in:
Peter Steinfeld 2021-03-08 08:21:30 -08:00
parent 535a4192a9
commit cfd7d8123a
2 changed files with 23 additions and 5 deletions
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10
flang/lib/Semantics/check-nullify.cpp
View File

@ -26,17 +26,17 @@ void NullifyChecker::Leave(const parser::NullifyStmt &nullifyStmt) {
std::visit(
common::visitors{
[&](const parser::Name &name) {
const Symbol &symbol{DEREF(name.symbol)};
if (context_.HasError(&symbol)) {
const Symbol *symbol{name.symbol};
if (context_.HasError(symbol)) {
// already reported an error
} else if (!IsVariableName(symbol) && !IsProcName(symbol)) {
} else if (!IsVariableName(*symbol) && !IsProcName(*symbol)) {
messages.Say(name.source,
"name in NULLIFY statement must be a variable or procedure pointer name"_err_en_US);
} else if (!IsPointer(symbol)) { // C951
} else if (!IsPointer(*symbol)) { // C951
messages.Say(name.source,
"name in NULLIFY statement must have the POINTER attribute"_err_en_US);
} else if (pure) {
CheckDefinabilityInPureScope(messages, symbol, scope, *pure);
CheckDefinabilityInPureScope(messages, *symbol, scope, *pure);
}
},
[&](const parser::StructureComponent &structureComponent) {

18
flang/test/Semantics/nullify02.f90
View File

@ -29,3 +29,21 @@ Nullify(prp)
Nullify(maxvalue)
End Program
! Make sure that the compiler doesn't crash when NULLIFY is used in a context
! that has reported errors
module badNullify
interface
module function ptrFun()
integer, pointer :: ptrFun
end function
end interface
contains
!ERROR: 'ptrfun' was not declared a separate module procedure
module function ptrFun()
integer, pointer :: ptrFun
real :: realVar
nullify(ptrFun)
nullify(realVar)
end function
end module