let's call this progress on #321 but not a resolution. following up on investigation by @kpreisser I have changed the problematic overload of raw.sqlite3_prepare_v2() to call a different overload of same in the provider to avoid creating a span from a pointer. with this change, I can run the issue321 repro app at 20 iterations on net461 without a failure. so this seems to confirm with @kpreisser said, but now every case where I create a span from a pointer needs to be reviewed for this kind of lifetime issue.

Author: ericsink

Directory.Build.props

@@ -4,9 +4,9 @@
     <Copyright>Copyright 2014-2020 SourceGear, LLC</Copyright>
     <Company>SourceGear</Company>
     <Authors>Eric Sink</Authors>
-    <Version>2.0.4-pre20200603163150</Version>
-    <AssemblyVersion>2.0.4.884</AssemblyVersion>
-    <FileVersion>2.0.4.884</FileVersion>
+    <Version>2.0.4-pre20200604104406</Version>
+    <AssemblyVersion>2.0.4.885</AssemblyVersion>
+    <FileVersion>2.0.4.885</FileVersion>
     <Description>SQLitePCLRaw is a Portable Class Library (PCL) for low-level (raw) access to SQLite</Description>
     <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>
     <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>

src/SQLitePCLRaw.core/raw.cs

@@ -736,8 +736,10 @@ static public int sqlite3_prepare_v2(sqlite3 db, utf8z sql, out sqlite3_stmt stm
 
         static public int sqlite3_prepare_v2(sqlite3 db, string sql, out sqlite3_stmt stmt, out string tail)
         {
-            int rc = sqlite3_prepare_v2(db, sql.to_utf8z(), out stmt, out var sp_tail);
-            tail = sp_tail.utf8_to_string();
+            var ba = sql.to_utf8_with_z();
+            var sp = new ReadOnlySpan<byte>(ba);
+            int rc = sqlite3_prepare_v2(db, sp, out stmt, out var sp_tail);
+            tail = utf8_span_to_string(sp_tail.Slice(0, sp_tail.Length - 1));
             return rc;
         }
 

test_nupkgs/issue321/repro.cs

@@ -94,7 +94,7 @@ static string RandomString(int length)
 
         public static void Main()
         {
-            var num = 10;
+            var num = 20;
             for (var i = 0; i<num; i++)
             {
                 Console.Write($"{i + 1} of {num}: ");