[libcxx-commits] [PATCH] D98412: [libcxx] Avoid intermediate string objects for substrings in windows operator/=

[Martin Storsjö via Phabricator via libcxx-commits]

mstorsjo created this revision.
mstorsjo requested review of this revision.
Herald added a project: libc++.
Herald added a reviewer: libc++.

Check that appends with a path object doesn't do allocations, even
on windows.

Suggested by Marek in D98398 <https://reviews.llvm.org/D98398>. The patch might apply without D98398 <https://reviews.llvm.org/D98398>
(depending on how much of the diff context has to match), but doesn't
make much sense until after that patch has landed.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D98412

Files:
  libcxx/include/filesystem
  libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp


Index: libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp
===================================================================
--- libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp
+++ libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp
@@ -179,6 +179,15 @@
     }
     assert(PathEq(LHS, E));
   }
+  {
+    path LHS(L); PathReserve(LHS, ReserveSize);
+    path RHS(R);
+    {
+      DisableAllocationGuard g;
+      LHS /= RHS;
+    }
+    assert(PathEq(LHS, E));
+  }
   // input iterator - For non-native char types, appends needs to copy the
   // iterator range into a contiguous block of memory before it can perform the
   // code_cvt conversions.
Index: libcxx/include/filesystem
===================================================================
--- libcxx/include/filesystem
+++ libcxx/include/filesystem
@@ -1026,12 +1026,12 @@
     if (__p.has_root_directory()) {
       path __root_name_str = root_name();
       __pn_ = __root_name_str.native();
-      __pn_ += __p.__pn_.substr(__p_root_name_size);
+      __pn_ += __string_view(__p.__pn_).substr(__p_root_name_size);
       return *this;
     }
     if (has_filename() || (!has_root_directory() && is_absolute()))
       __pn_ += preferred_separator;
-    __pn_ += __p.__pn_.substr(__p_root_name_size);
+    __pn_ += __string_view(__p.__pn_).substr(__p_root_name_size);
     return *this;
   }
   template <class _Source>


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D98412.329918.patch
Type: text/x-patch
Size: 1491 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/libcxx-commits/attachments/20210311/a7549b76/attachment.bin>