From 8d0938c9de034ec550927ed1c58bbaf2ec9a5930 Mon Sep 17 00:00:00 2001
From: Luna Nova <git@lunnova.dev>
Date: Sat, 4 Oct 2025 19:41:46 -0700
Subject: [PATCH] minimal-bootstrap.musl11: add stdio_flush_on_exit.patch, drop
 always-flush.patch

The upstream version of this patch has been commented out
since 913e70d77b67722a5b3bd42f21b9ea4cc02046e9, due to
error: implicit declaration of function '__stdio_exit'

Revived this approach by updating the patch to forward declare.
---
 .../linux/minimal-bootstrap/musl/1.1.nix      |  7 +-
 .../minimal-bootstrap/musl/always-flush.patch | 12 ----
 .../musl/stdio_flush_on_exit.patch            | 71 +++++++++++++++++++
 3 files changed, 75 insertions(+), 15 deletions(-)
 delete mode 100644 pkgs/os-specific/linux/minimal-bootstrap/musl/always-flush.patch
 create mode 100644 pkgs/os-specific/linux/minimal-bootstrap/musl/stdio_flush_on_exit.patch

diff --git a/pkgs/os-specific/linux/minimal-bootstrap/musl/1.1.nix b/pkgs/os-specific/linux/minimal-bootstrap/musl/1.1.nix
index fc762a956aa2..b14082365652 100644
--- a/pkgs/os-specific/linux/minimal-bootstrap/musl/1.1.nix
+++ b/pkgs/os-specific/linux/minimal-bootstrap/musl/1.1.nix
@@ -54,9 +54,10 @@ let
       url = "${liveBootstrap}/patches/sigsetjmp.patch";
       hash = "sha256-wd2Aev1zPJXy3q933aiup5p1IMKzVJBquAyl3gbK4PU=";
     })
-    # HACK: always flush stdio immediately
-    # Do not remove atm, gcc 4.6 does not build without this patch applied.
-    ./always-flush.patch
+    # liveBootstrap/sysa/musl-1.1.24/patches/stdio_flush_on_exit.patch with forward declarations added
+    # to avoid `error: implicit declaration of function '__stdio_exit'`
+    # Required to fix buffered stdout being truncated on exit
+    ./stdio_flush_on_exit.patch
     (fetchurl {
       url = "${liveBootstrap}/patches/va_list.patch";
       hash = "sha256-UmcMIl+YCi3wIeVvjbsCyqFlkyYsM4ECNwTfXP+s7vg=";
diff --git a/pkgs/os-specific/linux/minimal-bootstrap/musl/always-flush.patch b/pkgs/os-specific/linux/minimal-bootstrap/musl/always-flush.patch
deleted file mode 100644
index cdeddf962d9d..000000000000
--- a/pkgs/os-specific/linux/minimal-bootstrap/musl/always-flush.patch
+++ /dev/null
@@ -1,12 +0,0 @@
-diff --git src/env/__libc_start_main.c src/env/__libc_start_main.c
-index 8fbe526..9476c22 100644
---- src/env/__libc_start_main.c
-+++ src/env/__libc_start_main.c
-@@ -91,6 +91,7 @@ static int libc_start_main_stage2(int (*main)(int,char **,char **), int argc, ch
- 	__libc_start_init();
- 
- 	/* Pass control to the application */
-+	setbuf(stdout, NULL);
- 	exit(main(argc, argv, envp));
- 	return 0;
- }
diff --git a/pkgs/os-specific/linux/minimal-bootstrap/musl/stdio_flush_on_exit.patch b/pkgs/os-specific/linux/minimal-bootstrap/musl/stdio_flush_on_exit.patch
new file mode 100644
index 000000000000..145c13b29611
--- /dev/null
+++ b/pkgs/os-specific/linux/minimal-bootstrap/musl/stdio_flush_on_exit.patch
@@ -0,0 +1,71 @@
+Initial patch version retrieved from
+https://git.stikonas.eu/andrius/live-bootstrap/src/commit/cd361e63f77842d9780303d63382eb686843c76b/sysa/musl-1.1.24/patches/stdio_flush_on_exit.patch
+
+SPDX-FileCopyrightText: 2021 Paul Dersey <pdersey@gmail.com>
+SPDX-FileCopyrightText: 2025 Luna Nova <git@lunnova.dev>
+
+SPDX-License-Identifier: MIT
+
+Make sure real __stdio_exit() is called on exit and not the dummy
+noop versions.  This fixes the issue of truncated output when redirecting
+output to a file or pipe.  It also fixes truncated output on programs
+that forget to call fclose()
+
+Adds forward declarations to avoid implicit declaration error.
+
+diff --git a/src/exit/exit.c b/src/exit/exit.c
+index a6869b37..a4164682 100644
+--- src/exit/exit.c
++++ src/exit/exit.c
+@@ -2,16 +2,10 @@
+ #include <stdint.h>
+ #include "libc.h"
+ 
+-static void dummy()
+-{
+-}
+-
+-/* atexit.c and __stdio_exit.c override these. the latter is linked
+- * as a consequence of linking either __toread.c or __towrite.c. */
+-weak_alias(dummy, __funcs_on_exit);
+-weak_alias(dummy, __stdio_exit);
+-weak_alias(dummy, _fini);
++void __funcs_on_exit(void);
++void __stdio_exit(void);
++void _fini(void);
+ 
+ extern weak hidden void (*const __fini_array_start)(void), (*const __fini_array_end)(void);
+ 
+ static void libc_exit_fini(void)
+diff --git a/src/internal/stdio_impl.h b/src/internal/stdio_impl.h
+index d7398f59..69141813 100644
+--- src/internal/stdio_impl.h
++++ src/internal/stdio_impl.h
+@@ -47,9 +47,9 @@ struct _IO_FILE {
+ 	struct __locale_struct *locale;
+ };
+ 
+-extern hidden FILE *volatile __stdin_used;
+-extern hidden FILE *volatile __stdout_used;
+-extern hidden FILE *volatile __stderr_used;
++extern FILE *volatile __stdin_used;
++extern FILE *volatile __stdout_used;
++extern FILE *volatile __stderr_used;
+ 
+ hidden int __lockfile(FILE *);
+ hidden void __unlockfile(FILE *);
+diff --git a/src/stdio/__stdio_exit.c b/src/stdio/__stdio_exit.c
+index a5e42c67..5947a141 100644
+--- src/stdio/__stdio_exit.c
++++ src/stdio/__stdio_exit.c
+@@ -1,10 +1,5 @@
+ #include "stdio_impl.h"
+ 
+-static FILE *volatile dummy_file = 0;
+-weak_alias(dummy_file, __stdin_used);
+-weak_alias(dummy_file, __stdout_used);
+-weak_alias(dummy_file, __stderr_used);
+-
+ static void close_file(FILE *f)
+ {
+ 	if (!f) return;