[gcc r11-9252] libphobos: Increase size of defaultStackPages on OSX X86_64 targets.

[gcc r11-9252] libphobos: Increase size of defaultStackPages on OSX X86_64 targets.

[Iain Buclaw]

https://gcc.gnu.org/g:dc3630e05d7df3d9a93400e33710dd19be207da3

commit r11-9252-gdc3630e05d7df3d9a93400e33710dd19be207da3
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Fri Nov 19 14:43:07 2021 +0100

    libphobos: Increase size of defaultStackPages on OSX X86_64 targets.
    
    As of macOS 11, libunwind now requires more stack space than 16k, so
    default to a larger stack size. This is only applied to X86 as the
    PAGESIZE is still 4k, however on AArch64 it is 16k.
    
    libphobos/ChangeLog:
    
            * libdruntime/core/thread/fiber.d (defaultStackPages): Increase size
            on OSX X86_64 targets.
    
    (cherry picked from commit f316727e5f6a4c58b63bdee9ad6be785f97f5ee7)

Diff:
---
 libphobos/libdruntime/core/thread/fiber.d | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libphobos/libdruntime/core/thread/fiber.d b/libphobos/libdruntime/core/thread/fiber.d
index f4c04ce7358..2f90f179edb 100644
--- a/libphobos/libdruntime/core/thread/fiber.d
+++ b/libphobos/libdruntime/core/thread/fiber.d
@@ -595,6 +595,16 @@ class Fiber
         // the existence of debug symbols and other conditions. Avoid causing
         // stack overflows by defaulting to a larger stack size
         enum defaultStackPages = 8;
+    else version (OSX)
+    {
+        version (X86_64)
+            // libunwind on macOS 11 now requires more stack space than 16k, so
+            // default to a larger stack size. This is only applied to X86 as
+            // the PAGESIZE is still 4k, however on AArch64 it is 16k.
+            enum defaultStackPages = 8;
+        else
+            enum defaultStackPages = 4;
+    }
     else
         enum defaultStackPages = 4;