RFR: Improve missing symbols handling

[Henry Jen]

The current implementation behave correctly as expected, but reading LibraryLookupFilter feels wrong. It depends on the fact that linkCheckPaths is initialized to java.library.path when -l is specified but not -L in Main.java.

At least we can do is to add following change,

--- a/src/jdk.jextract/share/classes/com/sun/tools/jextract/LibraryLookupFilter.java
+++ b/src/jdk.jextract/share/classes/com/sun/tools/jextract/LibraryLookupFilter.java
@@ -86,8 +86,9 @@
     }

     private void initSymChecker(List<String> linkCheckPaths) {
-        if (!libraryNames.isEmpty() && !linkCheckPaths.isEmpty()) {
+        if (!libraryNames.isEmpty()) {
             try {
+                assert !linkCheckPaths.isEmpty();
                 Library[] libs = loadLibraries(MethodHandles.lookup(),
                         linkCheckPaths.toArray(new String[0]),
                         libraryNames.toArray(new String[0]));

Cheers,
Henry

> On May 3, 2019, at 10:02 AM, Henry Jen <henry.jen at oracle.com> wrote:
> 
> Correct.
> 
> Cheers,
> Henry
> 
> 
>> On May 3, 2019, at 10:00 AM, Maurizio Cimadamore <maurizio.cimadamore at oracle.com> wrote:
>> 
>> Seems like an useful follow up. Just to make sure I understand, if -l is specified, we get same behavior as before. If -l is NOT specified, then the behavior would differ (as we now do the check), and therefore we need the 'ignore' option explicitly, if we want to suppress logging. Right?
>> 
>> Maurizio
>> 
>> 
>> 
>> 
>> 
>> On 03/05/2019 17:43, Henry Jen wrote:
>>> Hi,
>>> 
>>> Please review a webrev[1] that add the missing —missing-symbols warn support, and turn on symbol checking against default library by default.
>>> 
>>> This is kind of a follow up to JDK-8223247, as that simply assume we are using the default libraries within JVM if no -l option is provided. This webrev now will
>>> 
>>> - Same behavior as before if both -l and -L are provided.
>>> - Symbol check is turned on always. If there is no -l provided, jextract will check symbols against the default library.
>>> - Default is to issue warnings without -l, exclude with explicit -l. This is mostly backward compatible as it doesn’t change generated code/classes, but show warnings to inform user about potential missing libraries.
>>> 
>>> To be 100% compatible with before, use '—missing-symbols ignore’
>>> 
>>> Thoughts?
>>> 
>>> Cheers,
>>> Henry
>>> 
>>> [1] http://cr.openjdk.java.net/~henryjen/panama/missingSymbols/webrev/
>