* made intialisation of FGeneralCriticalSection thread-safe

  * fixed a (harmless) use of an uninitialised variable

git-svn-id: trunk@45380 -

packages/fpmkunit/src/fpmkunit.pp

@@ -6787,27 +6787,37 @@ begin
   if APackage.NeedLibC or
      (Defaults.OS=linux) then
     begin
-    if FCachedlibcPath='' then
-      begin
-      s:=GetDefaultLibGCCDir(Defaults.CPU, Defaults.OS,ErrS);
-      if s='' then
-        Log(vlWarning, SWarngcclibpath +' '+ErrS)
-      else
+      if FCachedlibcPath='' then
         begin
+          s:=GetDefaultLibGCCDir(Defaults.CPU, Defaults.OS,ErrS);
+          if s='' then
+            Log(vlWarning, SWarngcclibpath +' '+ErrS)
+          else
+            begin
 {$ifndef NO_THREADING}
-        EnterCriticalsection(FGeneralCriticalSection);
-        try
+              EnterCriticalsection(FGeneralCriticalSection);
+              { prevent FCachedlibcPath getting freed by thread 2 while thread 1 is
+                concatenating it to -Fl below }
+              try
+                if volatile(FCachedlibcPath)='' then
+                  begin
 {$endif NO_THREADING}
-          FCachedlibcPath:=s;
+                    FCachedlibcPath:=s;
 {$ifndef NO_THREADING}
-        finally
-          LeaveCriticalsection(FGeneralCriticalSection);
-        end;
+                  end;
+              finally
+                LeaveCriticalsection(FGeneralCriticalSection);
+              end;
 {$endif NO_THREADING}
-        end;
-      end;
+            end;
+        end
+      else
+        { make sure we don't access the contents of the string before they've been
+          synchronised from the thread that wrote them; the critical section there
+          acts as a read/write barrier }
+        ReadBarrier;
 
-    Args.Add('-Fl'+FCachedlibcPath);
+      Args.Add('-Fl'+volatile(FCachedlibcPath));
     end;
 
   // Custom options which are added by dependencies
@@ -7085,7 +7095,7 @@ begin
         end
       else
         begin
-          S:=GetCompilerCommand(APackage,ATarget,Env);
+          S:=GetCompilerCommand(APackage,ATarget,nil);
           ExecuteCommand(GetCompiler,S,nil);
         end;
       If Assigned(ATarget.AfterCompile) then