Merge pull request #6258 from obsidiansystems/gcc-bug-ergonomics

Remove bug-avoiding `StoreConfig *` casts for settings

(cherry picked from commit e3febfcd532adb23ca05ac465a2b907d6f1a3529)
Change-Id: Ifeae276582fdbc781a38581df9de3da67a7e7bf9

1 files changed, 64 insertions, 0 deletions

diff --git a/m4/gcc_bug_80431.m4 b/m4/gcc_bug_80431.m4
new file mode 100644
index 000000000..e42f01956
--- /dev/null
+++ b/m4/gcc_bug_80431.m4
@@ -0,0 +1,64 @@
+# Ensure that this bug is not present in the C++ toolchain we are using.
+#
+# URL for bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80431
+#
+# The test program is from that issue, with only a slight modification
+# to set an exit status instead of printing strings.
+AC_DEFUN([ENSURE_NO_GCC_BUG_80431],
+[
+  AC_MSG_CHECKING([that GCC bug 80431 is fixed])
+  AC_LANG_PUSH(C++)
+  AC_RUN_IFELSE(
+    [AC_LANG_PROGRAM(
+      [[
+        #include <cstdio>
+
+        static bool a = true;
+        static bool b = true;
+
+        struct Options { };
+
+        struct Option
+        {
+            Option(Options * options)
+            {
+                a = false;
+            }
+
+            ~Option()
+            {
+                b = false;
+            }
+        };
+
+        struct MyOptions : Options { };
+
+        struct MyOptions2 : virtual MyOptions
+        {
+            Option foo{this};
+        };
+      ]],
+      [[
+        {
+            MyOptions2 opts;
+        }
+        return (a << 1) | b;
+      ]])],
+    [status_80431=0],
+    [status_80431=$?],
+    [
+      # Assume we're bug-free when cross-compiling
+    ])
+  AC_LANG_POP(C++)
+  AS_CASE([$status_80431],
+    [0],[
+      AC_MSG_RESULT(yes)
+    ],
+    [2],[
+      AC_MSG_RESULT(no)
+      AC_MSG_ERROR(Cannot build Nix with C++ compiler with this bug)
+    ],
+    [
+      AC_MSG_RESULT(unexpected result $status_80431: not expected failure with bug, ignoring)
+    ])
+])