Avoid repeated calls cppu::detail::loadModule -> osl_getModuleURLFromAddress

...where the latter are reportedly expensive.  Both
<https://gerrit.libreoffice.org/#/c/75162/> "tdf#121740 related, cache external
mapping in cppu::loadExternal" and <https://gerrit.libreoffice.org/#/c/82261/>
"tdf#121740 add cache to win osl_getModuleURLFromAddress" attempted to reduce
the costs observed when loading one specific document by introducing caches
below cppu::detail::loadModule's call to osl::Module::loadRelative.

On the other hand, this change reduces the number of calls to
osl_getModuleURLFromAddress by computing the base URI in
cppu::detail::loadModule only once.  For my local Linux --enable-dbgutil build,
for `instdir/program/soffice '109340 class14.ppt'` and then exiting LO again
(with the document attached at
<https://bugs.documentfoundation.org/show_bug.cgi?id=121740#c0>), this reduces
the number of calls to osl_getModuleURLFromAddress from 3775 to 22.

(Many of those calls originated from cppu::getCaughtException or
cppu::throwException, as in

  osl_getModuleURLFromAddress
  osl_getModuleURLFromFunctionAddress
  osl::Module::getUrlFromAddress
  osl_loadModuleRelative
  osl::Module::loadRelative
  cppu::detail::loadModule
  cppu::loadModule
  cppu::loadExternalMapping
  uno_getMapping
  com::sun:⭐:uno::Mapping::Mapping
  cppu::throwException

.)

Unfortunately, this needs to duplicate functionality from osl_loadModuleRelative
(sal/osl/all/loadmodulerelative.cxx) somewhat, as the stable SAL interface only
offers functionality to load relative to a given function, not relative to a
given base URI.  (And extending the stable SAL interface for this one use is not
worth the maintenance costs.)

Change-Id: Ib58814136d11c67d1419b0224d12e30bb710e613
Reviewed-on: https://gerrit.libreoffice.org/82290
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

cppu/source/uno/loadmodule.cxx

@@ -20,10 +20,15 @@
 
 #include <sal/config.h>
 
+#include <cassert>
+
 #include <osl/module.h>
 #include <osl/module.hxx>
+#include <rtl/malformeduriexception.hxx>
+#include <rtl/uri.hxx>
 #include <rtl/ustrbuf.hxx>
 #include <rtl/ustring.hxx>
+#include <sal/log.hxx>
 
 #include "loadmodule.hxx"
 
@@ -32,14 +37,34 @@ namespace cppu { namespace detail {
 #ifndef DISABLE_DYNLOADING
 
 bool loadModule(osl::Module& rModule, OUString const & name) {
+    static OUString base = [] {
+            OUString url;
+            if (!osl::Module::getUrlFromAddress(
+                    reinterpret_cast<oslGenericFunction>(&loadModule), url))
+            {
+                SAL_WARN("cppu", "osl::Module::getUrlFromAddress failed");
+                return OUString();
+            }
+            assert(!url.isEmpty());
+            return url;
+        }();
+    if (base.isEmpty()) {
+        SAL_INFO("cppu", "osl::Module::getUrlFromAddress had failed");
+        return false;
+    }
     OUString b =
 #if defined SAL_DLLPREFIX
         SAL_DLLPREFIX +
 #endif
         name +
         SAL_DLLEXTENSION;
-    return rModule.loadRelative(
+    try {
-        reinterpret_cast< oslGenericFunction >(&loadModule),
+        b = rtl::Uri::convertRelToAbs(base, b);
+    } catch (rtl::MalformedUriException & e) {
+        SAL_INFO("cppu", "rtl::MalformedUriException <" << e.getMessage() << ">");
+        return false;
+    }
+    return rModule.load(
         b,
         SAL_LOADMODULE_GLOBAL | SAL_LOADMODULE_LAZY);
 }