Adapt o3tl::span to P1872R0

..."span should have size_type, not index_type"
(<http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1872r0.pdf>), as
implemented by libc++ since <https://github.com/llvm/llvm-project/commit/
1466335cf4b2854a0be1defcf279fe50772bad6f> "[libc++][P1872] span should have
size_type, not index_type."

All uses of index_type had been added to mitigate the previous std::span change
from signed (ptrdiff_t) to unsigned (size_t) index_type, see
6ef8420fdbf8dff16de13147c5ab833bc5e01121 "Adapt o3tl::span to updated C++2a
std::span".  There is no easy solution to transparently support all three
std::span variants currently out there (signed index_type, unsigned index_type,
unsigned size_type), without causing compilation failures due to
CPPUNIT_ASSERT_EQUAL with arguments of different types, or compiler warnings
about mixed signed/unsigned comparisons.  So rule out the oldest std::span
variant (signed index_type) in configure.ac (so that o3tl::span will use its
own hand-rolled code in that case) and simplify the uses of index_type to
std::size_t (as had already been mentioned in
6ef8420fdbf8dff16de13147c5ab833bc5e01121).

Change-Id: I6ddf424ffb7941da3f69ad66fd29ecd35f09afae
Reviewed-on: https://gerrit.libreoffice.org/84652
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/o3tl/qa/test-span.cxx b/o3tl/qa/test-span.cxx
index 7ec67fa7fd91..3cb78ace1db2 100644
--- a/o3tl/qa/test-span.cxx
+++ b/o3tl/qa/test-span.cxx
@@ -9,6 +9,7 @@
 
 #include <sal/config.h>
 
+#include <cstddef>
 #include <utility>
 
 #include <cppunit/TestAssert.h>
@@ -42,7 +43,7 @@ private:
         CPPUNIT_ASSERT_EQUAL(3, *v.crbegin());
         CPPUNIT_ASSERT_EQUAL(
             o3tl::span<int>::difference_type(3), v.crend() - v.crbegin());
-        CPPUNIT_ASSERT_EQUAL(o3tl::span<int>::index_type(3), v.size());
+        CPPUNIT_ASSERT_EQUAL(std::size_t(3), v.size());
         CPPUNIT_ASSERT(!v.empty());
         CPPUNIT_ASSERT_EQUAL(2, v[1]);
         CPPUNIT_ASSERT_EQUAL(1, *v.data());
@@ -52,8 +53,8 @@ private:
             o3tl::span<int const> v1( d1 );
             o3tl::span<int const> v2( d2 );
             std::swap(v1, v2);
-            CPPUNIT_ASSERT_EQUAL(o3tl::span<int>::index_type(4), v1.size());
-            CPPUNIT_ASSERT_EQUAL(o3tl::span<int>::index_type(2), v2.size());
+            CPPUNIT_ASSERT_EQUAL(std::size_t(4), v1.size());
+            CPPUNIT_ASSERT_EQUAL(std::size_t(2), v2.size());
         }
     }
 };