From 0c796adb87491359dcf56efc75fde763e43b733e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Wed, 22 Apr 2026 15:30:58 +0200
Subject: [PATCH] zig cc: define __CRT__NO_INLINE for MinGW-w64 targets

See added comment for why.
---
 src/Compilation.zig | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/Compilation.zig b/src/Compilation.zig
index e8948ef112..7f26ac5c1b 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -6367,6 +6367,13 @@ fn addCommonCCArgs(
                     try argv.append(
                         try std.fmt.allocPrint(arena, "-D_WIN32_WINNT=0x{x:0>4}", .{minver}),
                     );
+
+                    // MinGW-w64's inline functions in headers (e.g. `fabs`), which are emitted with `linkonce_odr`
+                    // linkage, sometimes cause duplicate symbol errors due to us providing the same symbols with
+                    // `weak` linkage in compiler-rt or libzigc. So just disable them. Besides, they undermine the
+                    // goal of moving more libc code to Zig, and they're also just kind of unnecessary since LLVM is
+                    // perfectly capable of recognizing and optimizing libcalls.
+                    try argv.append("-D__CRT__NO_INLINE");
                 } else if (target.isFreeBSDLibC()) {
                     // https://docs.freebsd.org/en/books/porters-handbook/versions
                     const min_ver = target.os.version_range.semver.min;