From cf59f89bfb0f411fd4e4a022e4a5bd92efcdd58b Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Tue, 15 Apr 2025 22:29:26 +0300
Subject: [PATCH] LibC: Rework constructor/destructor calling

constructors are now called in _init_libc instead of crt0

destructors are now registered with atexit() instead of called manually
---
 userspace/libraries/LibC/arch/i686/crt0.S   | 34 +++++++++------------
 userspace/libraries/LibC/arch/x86_64/crt0.S | 23 ++++++--------
 userspace/libraries/LibC/stdlib.cpp         |  3 --
 userspace/libraries/LibC/unistd.cpp         | 23 +++++++++++++-
 4 files changed, 46 insertions(+), 37 deletions(-)

diff --git a/userspace/libraries/LibC/arch/i686/crt0.S b/userspace/libraries/LibC/arch/i686/crt0.S
index f50cdfb4..a1bb0202 100644
--- a/userspace/libraries/LibC/arch/i686/crt0.S
+++ b/userspace/libraries/LibC/arch/i686/crt0.S
@@ -3,9 +3,9 @@
 .global _start
 _start:
 	pushl $0
-	pushl %edi
-	pushl %esi
 	pushl %edx
+	pushl %esi
+	pushl %edi
 
 	# STACK LAYOUT
 	#   null
@@ -15,27 +15,21 @@ _start:
 
 	xorl %ebp, %ebp
 
-	# init libc (envp already as argument)
+	pushl $__fini_array_end
+	pushl $__fini_array_start
+	pushl $_fini
+
+	pushl $__init_array_end
+	pushl $__init_array_start
+	pushl $_init
+
+	pushl %edx
+
 	call _init_libc
 
-	# call global constructors
-	movl $_init, %eax
-	testl %eax, %eax
-	jz 1f
-	call *%eax
- 1:
+	addl $(4 * 8), %esp
 
-	movl $__init_array_start, %ebx
-	jmp 2f
- 1: call *(%ebx)
-	addl $4, %ebx
- 2: cmpl $__init_array_end, %ebx
-	jne 1b
-
-	# call main
-	movl 0(%esp), %eax
-	xchgl %eax, 8(%esp)
-	movl %eax, (%esp)
+	# argc, argv, envp already on stack
 	call main
 
 	subl $12, %esp
diff --git a/userspace/libraries/LibC/arch/x86_64/crt0.S b/userspace/libraries/LibC/arch/x86_64/crt0.S
index b5b543c9..36d4a1da 100644
--- a/userspace/libraries/LibC/arch/x86_64/crt0.S
+++ b/userspace/libraries/LibC/arch/x86_64/crt0.S
@@ -17,21 +17,18 @@ _start:
 
 	# init libc
 	movq 0(%rsp), %rdi
+
+	pushq $__fini_array_end
+	pushq $__fini_array_start
+	pushq $_fini
+
+	pushq $__init_array_end
+	pushq $__init_array_start
+	pushq $_init
+
 	call _init_libc
 
-	# call global constructors
-	movq $_init, %rax
-	testq %rax, %rax
-	jz 1f
-	call *%rax
- 1:
-
-	movq $__init_array_start, %rbx
-	jmp 2f
- 1: call *(%rbx)
-	addq $8, %rbx
- 2: cmpq $__init_array_end, %rbx
-	jne 1b
+	addq $(6 * 8), %rsp
 
 	# call main
 	movq 16(%rsp), %rdi
diff --git a/userspace/libraries/LibC/stdlib.cpp b/userspace/libraries/LibC/stdlib.cpp
index 466009ab..89ddfcb2 100644
--- a/userspace/libraries/LibC/stdlib.cpp
+++ b/userspace/libraries/LibC/stdlib.cpp
@@ -23,8 +23,6 @@ char** __environ;
 weak_alias(__environ, environ);
 static bool s_environ_malloced = false;
 
-extern "C" __attribute__((weak)) void _fini();
-
 void abort(void)
 {
 	sigset_t set;
@@ -43,7 +41,6 @@ void exit(int status)
 {
 	fflush(nullptr);
 	__cxa_finalize(nullptr);
-	if (_fini) _fini();
 	_exit(status);
 	ASSERT_NOT_REACHED();
 }
diff --git a/userspace/libraries/LibC/unistd.cpp b/userspace/libraries/LibC/unistd.cpp
index 41779ec2..404388df 100644
--- a/userspace/libraries/LibC/unistd.cpp
+++ b/userspace/libraries/LibC/unistd.cpp
@@ -16,12 +16,33 @@
 #include <termios.h>
 #include <unistd.h>
 
+struct init_funcs_t
+{
+	void (*func)();
+	void (**array_start)();
+	void (**array_end)();
+};
+
 extern "C" char** environ;
 
-extern "C" void _init_libc(char** _environ)
+extern "C" void _init_libc(char** environ, init_funcs_t init_funcs, init_funcs_t fini_funcs)
 {
 	if (::environ == nullptr)
 		::environ = environ;
+
+	// call global constructors
+	if (init_funcs.func)
+		init_funcs.func();
+	const size_t init_array_count = init_funcs.array_end - init_funcs.array_start;
+	for (size_t i = 0; i < init_array_count; i++)
+		init_funcs.array_start[i]();
+
+	// register global destructors
+	const size_t fini_array_count = fini_funcs.array_end - fini_funcs.array_start;
+	for (size_t i = 0; i < fini_array_count; i++)
+		atexit(fini_funcs.array_start[i]);
+	if (fini_funcs.func)
+		atexit(fini_funcs.func);
 }
 
 void _exit(int status)