[gcc r11-10115] libstdc++: Fix cast in source_location::current() [PR104602]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:ed377f0fb3419fceed25ae378aca2efca1a6b79d

commit r11-10115-ged377f0fb3419fceed25ae378aca2efca1a6b79d
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Feb 24 21:33:44 2022 +0000

    libstdc++: Fix cast in source_location::current() [PR104602]
    
    This fixes a problem for Clang, which is going to return a non-void
    pointer from __builtin_source_location(). The current definition of
    std::source_location::current() converts that to void* and then has to
    cast it back again in the body (which makes it invalid in a constant
    expression). By using the actual type of the returned pointer, we avoid
    the problematic cast for Clang.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/104602
            * include/std/source_location (source_location::current): Use
            deduced type of __builtin_source_location().
    
    (cherry picked from commit 41cbcf53dc60b7434b9ee059b3a734a47f5bf212)

Diff:
---
 libstdc++-v3/include/std/source_location | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/source_location b/libstdc++-v3/include/std/source_location
index 6cf6d7949cf..0a101c3df11 100644
--- a/libstdc++-v3/include/std/source_location
+++ b/libstdc++-v3/include/std/source_location
@@ -43,12 +43,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   {
   private:
     using uint_least32_t = __UINT_LEAST32_TYPE__;
+    using __builtin_ret_type = decltype(__builtin_source_location());
 
   public:
 
     // [support.srcloc.cons], creation
     static consteval source_location
-    current(const void* __p = __builtin_source_location()) noexcept
+    current(__builtin_ret_type __p = __builtin_source_location()) noexcept
     {
       source_location __ret;
       __ret._M_impl = static_cast <const __impl*>(__p);