[flang][OpenMP] Fix goto within SECTION (llvm#144502)

Previously we didn't push any context for SECTION and they are not
modelled with differing scopes and so goto detection couldn't tell that
GOTOs between two SECTIONs were between constructs rather than just
staying inside of the parent SECTIONS construct.

Fixes llvm#143231

Author: tblah

flang/lib/Semantics/resolve-directives.cpp

@@ -384,6 +384,9 @@ class OmpAttributeVisitor : DirectiveAttributeVisitor<llvm::omp::Directive> {
   bool Pre(const parser::OpenMPSectionsConstruct &);
   void Post(const parser::OpenMPSectionsConstruct &) { PopContext(); }
 
+  bool Pre(const parser::OpenMPSectionConstruct &);
+  void Post(const parser::OpenMPSectionConstruct &) { PopContext(); }
+
   bool Pre(const parser::OpenMPCriticalConstruct &critical);
   void Post(const parser::OpenMPCriticalConstruct &) { PopContext(); }
 
@@ -2003,6 +2006,12 @@ bool OmpAttributeVisitor::Pre(const parser::OpenMPSectionsConstruct &x) {
   return true;
 }
 
+bool OmpAttributeVisitor::Pre(const parser::OpenMPSectionConstruct &x) {
+  PushContext(x.source, llvm::omp::Directive::OMPD_section);
+  GetContext().withinConstruct = true;
+  return true;
+}
+
 bool OmpAttributeVisitor::Pre(const parser::OpenMPCriticalConstruct &x) {
   const auto &beginCriticalDir{std::get<parser::OmpCriticalDirective>(x.t)};
   const auto &endCriticalDir{std::get<parser::OmpEndCriticalDirective>(x.t)};
@@ -3024,8 +3033,13 @@ void OmpAttributeVisitor::CheckLabelContext(const parser::CharBlock source,
     const parser::CharBlock target, std::optional<DirContext> sourceContext,
     std::optional<DirContext> targetContext) {
   auto dirContextsSame = [](DirContext &lhs, DirContext &rhs) -> bool {
-    // Sometimes nested constructs share a scope but are different contexts
-    return (lhs.scope == rhs.scope) && (lhs.directive == rhs.directive);
+    // Sometimes nested constructs share a scope but are different contexts.
+    // The directiveSource comparison is for OmpSection. Sections do not have
+    // their own scopes and two different sections both have the same directive.
+    // Their source however is different. This string comparison is unfortunate
+    // but should only happen for GOTOs inside of SECTION.
+    return (lhs.scope == rhs.scope) && (lhs.directive == rhs.directive) &&
+        (lhs.directiveSource == rhs.directiveSource);
   };
   unsigned version{context_.langOptions().OpenMPVersion};
   if (targetContext &&

flang/test/Semantics/OpenMP/parallel-sections01.f90

@@ -35,6 +35,8 @@ program OmpConstructSections01
    !$omp section
    print *, "This is a single statement structured block"
    !$omp section
+   !ERROR: invalid branch into an OpenMP structured block
+   !ERROR: invalid branch leaving an OpenMP structured block
    open (10, file="random-file-name.txt", err=30)
    !ERROR: invalid branch into an OpenMP structured block
    !ERROR: invalid branch leaving an OpenMP structured block

flang/test/Semantics/OpenMP/sections-goto.f90

@@ -0,0 +1,11 @@
+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+! Regression test for #143231
+
+!$omp sections
+! ERROR: invalid branch into an OpenMP structured block
+! ERROR: invalid branch leaving an OpenMP structured block
+goto 10
+!$omp section
+10 print *, "Invalid jump"
+!$omp end sections
+end

flang/test/Semantics/OpenMP/sections02.f90

@@ -19,6 +19,8 @@ program OmpConstructSections01
    !$omp section
    print *, "This is a single statement structured block"
    !$omp section
+   !ERROR: invalid branch into an OpenMP structured block
+   !ERROR: invalid branch leaving an OpenMP structured block
    open (10, file="random-file-name.txt", err=30)
    !ERROR: invalid branch into an OpenMP structured block
    !ERROR: invalid branch leaving an OpenMP structured block