[Libreoffice] Reporting an error when loading of a component fails

 Hello,

 last week .docx support was broken because of a mistake during the gbuild 
changes and I wasted quite some time finding out what was wrong. As something 
similar had happened to me already before I'd like to apply the attached 
patches. However I have some issues with it:

- the error dialog that pops up just says 'General error. General input/output 
error.', which is completely unhelpful, however I don't feel like digging 
more for how to pass the information as far as the place where the dialog is 
shown, so I'd like to add at least debug output

- the debug output in the patch is done just using fprintf(stderr), as I 
cannot find anything that would simply log a debug message and not do more - 
is there anything like that in LO?

- osl_loadModule*() functions are plain C functions from stable API, so no 
overloading to add the extra argument for the error message, the best I've 
come up with was simply a wrapper around dlerror(), which I admit is not very 
nice API either, would there be any better approach?

-- 
 Lubos Lunak
 l.lunak@suse.cz

diff --git a/cppuhelper/source/shlib.cxx b/cppuhelper/source/shlib.cxx
index a979454..1beed1f 100644
--- a/cppuhelper/source/shlib.cxx
+++ b/cppuhelper/source/shlib.cxx
@@ -367,9 +367,14 @@ Reference< XInterface > SAL_CALL loadSharedLibComponentFactory(
         aModulePath.pData, SAL_LOADMODULE_LAZY | SAL_LOADMODULE_GLOBAL );
     if (! lib)
     {
-        throw loader::CannotActivateFactoryException(
-            OUSTR("loading component library failed: ") + aModulePath,
-            Reference< XInterface >() );
+        OUStringBuffer message = OUSTR("loading component library failed: ") + aModulePath;
+        if( const char* error = osl_loadModuleLastError())
+        {
+            message.appendAscii( " (" );
+            message.append( OStringToOUString( error, RTL_TEXTENCODING_UTF8 ));
+            message.appendAscii( ")" );
+        }
+        throw loader::CannotActivateFactoryException( message.makeStringAndClear(), Reference< 
XInterface >() );
     }
 
     Reference< XInterface > xRet;
diff --git a/sal/inc/osl/module.h b/sal/inc/osl/module.h
index 803b0b6..2a92d39 100644
--- a/sal/inc/osl/module.h
+++ b/sal/inc/osl/module.h
@@ -102,6 +102,16 @@ oslModule SAL_CALL osl_loadModuleAscii(const sal_Char *pModuleName, sal_Int32 
nR
 oslModule SAL_CALL osl_loadModuleRelative(
     oslGenericFunction baseModule, rtl_uString * relativePath, sal_Int32 mode);
 
+/**
+    Return an error message for the last error in any of the osl_loadModule*() functions,
+    or NULL if none.
+    @since 3.5.0
+*/
+// TODO 4.0: this is kind of retarded, the osl_loadModule functions themselves should provide
+// this, but this is stable API and C-only, so no simple extending is possible and I don't
+// feel like making the API even more ugly by introducing osl_loadModule*WithError() copies
+const char* SAL_CALL osl_loadModuleLastError();
+
 /** Retrieve the handle of an already loaded module.
 
     This function can be used to search for a function symbol in the process address space.
diff --git a/sal/osl/unx/module.c b/sal/osl/unx/module.c
index a5beea9..7b7ca6f 100644
--- a/sal/osl/unx/module.c
+++ b/sal/osl/unx/module.c
@@ -104,6 +104,11 @@ oslModule SAL_CALL osl_loadModuleAscii(const sal_Char *pModuleName, sal_Int32 
nR
     return NULL;
 }
 
+const char* SAL_CALL osl_loadModuleLastError()
+{
+    return dlerror();
+}
+
 /*****************************************************************************/
 /* osl_getModuleHandle */
 /*****************************************************************************/
diff --git a/sal/osl/w32/module.cxx b/sal/osl/w32/module.cxx
index a332d3a..1a906dd 100644
--- a/sal/osl/w32/module.cxx
+++ b/sal/osl/w32/module.cxx
@@ -144,6 +144,11 @@ oslModule SAL_CALL osl_loadModuleAscii(const sal_Char *pModuleName, sal_Int32 
nR
     return ret;
 }
 
+const char* SAL_CALL osl_loadModuleLastError()
+{
+    return NULL; // TODO
+}
+
 /*****************************************************************************/
 /* osl_getModuleHandle */
 /*****************************************************************************/
diff --git a/sal/util/sal.map b/sal/util/sal.map
index 152b023..b4367e2 100755
--- a/sal/util/sal.map
+++ b/sal/util/sal.map
@@ -609,6 +609,7 @@ LIBO_UDK_3.5 { # symbols available in >= LibO 3.5
     global:
         rtl_stringbuffer_remove;
         rtl_uStringbuffer_remove;
+        osl_loadModuleLastError;
 } UDK_3.10;
 
 PRIVATE_1.0 {

diff --git a/sfx2/source/doc/objstor.cxx b/sfx2/source/doc/objstor.cxx
index 31ee8f0..fca227b 100644
--- a/sfx2/source/doc/objstor.cxx
+++ b/sfx2/source/doc/objstor.cxx
@@ -2281,8 +2281,13 @@ sal_Bool SfxObjectShell::ExportTo( SfxMedium& rMedium )
             try{
             xExporter = uno::Reference< document::XExporter >
                 ( xFilterFact->createInstanceWithArguments( aFilterName, uno::Sequence < uno::Any 
> () ), uno::UNO_QUERY );
-            }catch(const uno::Exception&)
-                { xExporter.clear(); }
+            }catch(const uno::Exception& e)
+            {
+#if OSL_DEBUG_LEVEL > 0
+                fprintf( stderr, "%s\n", rtl::OUStringToOString( e.Message, RTL_TEXTENCODING_UTF8 
).getStr());
+#endif
+                xExporter.clear();
+            }
         }
     }