Ensure string_params doesn't get GC'd (#276)

* Update asyncresults.jl

* move to GC.@preserve & fix all usages

* fix whitespace

* fixup style

Author: krynju

src/asyncresults.jl

@@ -252,7 +252,9 @@ function async_execute(
     pointer_params = parameter_pointers(string_params)
 
     async_result = _async_execute(jl_conn; binary_format=binary_format, kwargs...) do jl_conn
-            _async_submit(jl_conn.conn, query, pointer_params; binary_format=binary_format)
+            GC.@preserve string_params _async_submit(
+                jl_conn.conn, query, pointer_params; binary_format=binary_format
+            )
         end
 
     return async_result

src/copy.jl

@@ -52,7 +52,9 @@ function execute(
         if parameters === nothing
             result = _execute(jl_conn.conn, copy.query)
         else
-            result = _execute(jl_conn.conn, copy.query, pointer_params)
+            result = GC.@preserve string_params _execute(
+                jl_conn.conn, copy.query, pointer_params
+            )
         end
         result_status = libpq_c.PQresultStatus(result)
 

src/results.jl

@@ -322,7 +322,9 @@ function execute(
     pointer_params = parameter_pointers(string_params)
 
     result = lock(jl_conn) do
-        _execute(jl_conn.conn, query, pointer_params; binary_format=binary_format)
+        GC.@preserve string_params _execute(
+            jl_conn.conn, query, pointer_params; binary_format=binary_format
+        )
     end
 
     return handle_result(

src/statements.jl

@@ -121,7 +121,7 @@ function execute(
     pointer_params = parameter_pointers(string_params)
 
     result = lock(stmt.jl_conn) do
-        _execute_prepared(
+        GC.@preserve string_params _execute_prepared(
             stmt.jl_conn.conn, stmt.name, pointer_params; binary_format=binary_format
         )
     end