From b1941c9f8a40b6aeb42d0ddc20af85c54a9bd80f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io>
Date: Fri, 2 Aug 2024 11:12:06 +0200
Subject: [PATCH] allow to c api with older c versions

In the FFI world we have many tools that are not gcc/clang and therefore
not always support the latest C standard. This fixes support with cffi
i.e. used in https://github.com/tweag/python-nix

(cherry picked from commit 739418504c4d2f28fb5f45151b1c83707c3571e2)
---
 src/libexpr-c/nix_api_expr.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/libexpr-c/nix_api_expr.h b/src/libexpr-c/nix_api_expr.h
index adf8b65b1..1764b49f3 100644
--- a/src/libexpr-c/nix_api_expr.h
+++ b/src/libexpr-c/nix_api_expr.h
@@ -14,6 +14,16 @@
 #include "nix_api_util.h"
 #include <stddef.h>
 
+#ifndef __has_c_attribute
+#  define __has_c_attribute(x) 0
+#endif
+
+#if __has_c_attribute(deprecated)
+#  define NIX_DEPRECATED(msg) [[deprecated(msg)]]
+#else
+#  define NIX_DEPRECATED(msg)
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -45,7 +55,7 @@ typedef struct EvalState EvalState; // nix::EvalState
  * @see nix_value_incref, nix_value_decref
  */
 typedef struct nix_value nix_value;
-[[deprecated("use nix_value instead")]] typedef nix_value Value;
+NIX_DEPRECATED("use nix_value instead") typedef nix_value Value;
 
 // Function prototypes
 /**