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authorStephan Bergmann <sbergman@redhat.com>2020-09-08 09:48:17 +0200
committerStephan Bergmann <sbergman@redhat.com>2020-09-16 23:02:09 +0200
commite6dfaf9f44f9939abc338c83b3024108431d0f69 (patch)
tree2e220510dc589fa4ce9b205696b9d0b58d38b60a /connectivity/source/drivers/evoab2
parenteb55bc5eae82873492cfd7577fb553b1c5abff6b (diff)
Turn OUStringLiteral into a consteval'ed, static-refcound rtl_uString
...from which an OUString can cheaply be instantiated. This is the OUString equivalent of 4b9e440c51be3e40326bc90c33ae69885bfb51e4 "Turn OStringLiteral into a consteval'ed, static-refcound rtl_String". Most remarks about that commit apply here too (this commit is just substantially bigger and a bit more complicated because there were so much more uses of OUStringLiteral than of OStringLiteral): The one downside is that OUStringLiteral now needs to be a template abstracting over the string length. But any uses for which that is a problem (e.g., as the element type of a container that would no longer be homogeneous, or in the signature of a function that shall not be turned into a template for one reason or another) can be replaced with std::u16string_view, without loss of efficiency compared to the original OUStringLiteral, and without loss of expressivity. The new OUStringLiteral ctor code would probably not be very efficient if it were ever executed at runtime, but it is intended to be only executed at compile time. Where available, C++20 "consteval" is used to statically ensure that. The intended use of the new OUStringLiteral is in all cases where an object that shall itself not be an OUString (e.g., because it shall be a global static variable for which the OUString ctor/dtor would be detrimental at library load/unload) must be converted to an OUString instance in at least one place. Other string literal abstractions could use std::u16string_view (or just plain char16_t const[N]), but interestingly OUStringLiteral might be more efficient than constexpr std::u16string_view even for such cases, as it should not need any relocations at library load time. For now, no existing uses of OUStringLiteral have been changed to some other abstraction (unless technically necessary as discussed above), and no additional places that would benefit from OUStringLiteral have been changed to use it. Global constexpr OUStringLiteral variables defined in an included file would be somewhat suboptimal, as each translation unit that uses them would create its own, unshared instance. The envisioned solution is to turn them into static data members of some class (and there may be a loplugin coming to find and fix affected places). Another approach that has been taken here in a few cases where such variables were only used in one .cxx anyway is to move their definitions from the .hxx into that one .cxx (in turn causing some files to become empty and get removed completely)---which also silenced some GCC -Werror=unused-variable if a variable from a .hxx was not used in some .cxx including it. To keep individual commits reasonably manageable, some consumers of OUStringLiteral in rtl/ustrbuf.hxx and rtl/ustring.hxx are left in a somewhat odd state for now, where they don't take advantage of OUStringLiteral's equivalence to rtl_uString, but just keep extracting its contents and copy it elsewhere. In follow-up commits, those consumers should be changed appropriately, making them treat OUStringLiteral like an rtl_uString or dropping the OUStringLiteral overload in favor of an existing (and cheap to use now) OUString overload, etc. In a similar vein, comparison operators between OUString and std::u16string_view have been added to the existing plethora of comparison operator overloads. It would be nice to eventually consolidate them, esp. with the overloads taking OUStringLiteral and/or char16_t const[N] string literals, but that appears tricky to get right without introducing new ambiguities. Also, a handful of places across the code base use comparisons between OUString and OUStringNumber, which are now ambiguous (converting the OUStringNumber to either OUString or std::u16string_view). For simplicity, those few places have manually been fixed for now by adding explicit conversion to std::u16string_view. Also some compilerplugins code needed to be adapted, and some of the compilerplugins/test cases have become irrelevant (and have been removed), as the tested code would no longer compile in the first place. sal/qa/rtl/strings/test_oustring_concat.cxx documents a workaround for GCC bug <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96878> "Failed class template argument deduction in unevaluated, parenthesized context". That place, as well as uses of OUStringLiteral in extensions/source/abpilot/fieldmappingimpl.cxx and i18npool/source/localedata/localedata.cxx, which have been replaced with OUString::Concat (and which is arguably a better choice, anyway), also caused failures with at least Clang 5.0.2 (but would not have caused failures with at least recent Clang 12 trunk, so appear to be bugs in Clang that have meanwhile been fixed). Change-Id: I34174462a28f2000cfeb2d219ffd533a767920b8 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/102222 Tested-by: Jenkins Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Diffstat (limited to 'connectivity/source/drivers/evoab2')
-rw-r--r--connectivity/source/drivers/evoab2/NDatabaseMetaData.cxx4
1 files changed, 3 insertions, 1 deletions
diff --git a/connectivity/source/drivers/evoab2/NDatabaseMetaData.cxx b/connectivity/source/drivers/evoab2/NDatabaseMetaData.cxx
index 65cb6a4fe8a5..97cdd9775c7f 100644
--- a/connectivity/source/drivers/evoab2/NDatabaseMetaData.cxx
+++ b/connectivity/source/drivers/evoab2/NDatabaseMetaData.cxx
@@ -26,6 +26,8 @@
#include <cstddef>
#include <string.h>
+#include <string_view>
+
#include "EApi.h"
using namespace connectivity::evoab;
@@ -978,7 +980,7 @@ Reference< XResultSet > SAL_CALL OEvoabDatabaseMetaData::getTableTypes( )
/* Don't need to change as evoab driver supports only table */
// there exists no possibility to get table types so we have to check
- static const OUStringLiteral sTableTypes[] =
+ static const std::u16string_view sTableTypes[] =
{
u"TABLE" // Currently we only support a 'TABLE' nothing more complex
};