From b80cad24840700ead20b59734916bf3d4d4ba87c Mon Sep 17 00:00:00 2001
From: Emil Tywoniak <Emil.Tywoniak@hightec-rt.com>
Date: Thu, 18 Jan 2024 14:16:52 +0100
Subject: [PATCH] libcxx: fix C++ builds with glibc <2.16 without aligned_alloc

---
 src/libcxx.zig | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/libcxx.zig b/src/libcxx.zig
index 7b2e612838..d47ec71a64 100644
--- a/src/libcxx.zig
+++ b/src/libcxx.zig
@@ -233,6 +233,13 @@ pub fn buildLibCXX(comp: *Compilation, prog_node: *std.Progress.Node) !void {
             try cflags.append("-D_LIBCPP_HAS_MUSL_LIBC");
         }
 
+        if (target.isGnuLibC()) {
+            // glibc 2.16 introduced aligned_alloc
+            if (target.os.version_range.linux.glibc.order(.{ .major = 2, .minor = 16, .patch = 0 }) == .lt) {
+                try cflags.append("-D_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION");
+            }
+        }
+
         if (target.os.tag == .wasi) {
             // WASI doesn't support exceptions yet.
             try cflags.append("-fno-exceptions");
@@ -433,6 +440,13 @@ pub fn buildLibCXXABI(comp: *Compilation, prog_node: *std.Progress.Node) !void {
             try cflags.append("-D_LIBCPP_HAS_MUSL_LIBC");
         }
 
+        if (target.isGnuLibC()) {
+            // glibc 2.16 introduced aligned_alloc
+            if (target.os.version_range.linux.glibc.order(.{ .major = 2, .minor = 16, .patch = 0 }) == .lt) {
+                try cflags.append("-D_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION");
+            }
+        }
+
         if (target_util.supports_fpic(target)) {
             try cflags.append("-fPIC");
         }