From 031c9ea85d5423ef1bb6b2647a77b8422b54c080 Mon Sep 17 00:00:00 2001
From: Robbin Ehn <rehn@rivosinc.com>
Date: Thu, 21 Mar 2024 11:40:56 +0100
Subject: [PATCH] windows logging

---
 src/hotspot/os/windows/os_windows.cpp | 36 ++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/src/hotspot/os/windows/os_windows.cpp b/src/hotspot/os/windows/os_windows.cpp
index 2ddebc9bf6dee..675e7d1952525 100644
--- a/src/hotspot/os/windows/os_windows.cpp
+++ b/src/hotspot/os/windows/os_windows.cpp
@@ -1279,8 +1279,33 @@ void  os::dll_unload(void *lib) {
   }
 }
 
+static size_t format_message_fixup(char* buf, size_t end) {
+  if (end > 3) {
+    if (buf[end - 1] == '\n') end--;
+    if (buf[end - 1] == '\r') end--;
+    if (buf[end - 1] == '.')  end--;
+    buf[end] = '\0';
+  }
+  return end;
+}
+
 void* os::dll_lookup(void *lib, const char *name) {
-  return (void*)::GetProcAddress((HMODULE)lib, name);
+  void* ret = ::GetProcAddress((HMODULE)lib, name);
+  DWORD errval;
+  if ((errval = GetLastError()) != 0) {
+    char* buf[512];
+    size_t n = (size_t)FormatMessage(
+                                     FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,
+                                     nullptr,
+                                     errval,
+                                     0,
+                                     buf,
+                                     (DWORD)sizeof(buf),
+                                     nullptr);
+    format_message_fixup(buf, n);
+    log_debug(os)("Symbol %s not found in dll: %s", name, buf);
+  }
+  return ret;
 }
 
 // Directory routines copied from src/win32/native/java/io/dirent_md.c
@@ -2165,14 +2190,7 @@ size_t os::lasterror(char* buf, size_t len) {
                                      buf,
                                      (DWORD)len,
                                      nullptr);
-    if (n > 3) {
-      // Drop final '.', CR, LF
-      if (buf[n - 1] == '\n') n--;
-      if (buf[n - 1] == '\r') n--;
-      if (buf[n - 1] == '.') n--;
-      buf[n] = '\0';
-    }
-    return n;
+    return format_message_fixup(buf, n);
   }
 
   if (errno != 0) {