libc+tests+tools: Call global constructors in userspace code

libc/src/arch/x86_64/crt0.S

@@ -3,6 +3,8 @@
 .global _start
 .extern exit
 .extern libc_init
+.extern _init
+.extern _fini
 _start:
 	# Set up end of the stack frame linked list.
 	movq $0, %rbp
@@ -26,6 +28,11 @@ _start:
 	# Run main
 	call main
 
+	# Store the exit code before calling _fini.
+	push %rax
+
+	call _fini
+
 	# Terminate the process with the exit code.
-	movl %eax, %edi
+	pop %rdi
 	call exit

libc/src/init.cpp

@@ -7,6 +7,14 @@ extern char** environ;
 extern "C" FILE* _fdopen_impl(int, const char*, int);
 extern "C" void _init_stdio();
 
+typedef void initfunc_t(void);
+extern initfunc_t *__init_array_start[], *__init_array_end[];
+
+static void handle_init_array(void)
+{
+    for (initfunc_t** p = __init_array_start; p != __init_array_end; p++) (*p)();
+}
+
 extern "C"
 {
     void libc_init(int argc, char** argv, int envc, char** envp)
@@ -19,5 +27,7 @@ extern "C"
         stdin = _fdopen_impl(STDIN_FILENO, "r", _IOLBF);
         stdout = _fdopen_impl(STDOUT_FILENO, "w", _IOLBF);
         stderr = _fdopen_impl(STDERR_FILENO, "w", _IONBF);
+
+        handle_init_array();
     }
 }

tests/CMakeLists.txt

@@ -23,6 +23,7 @@ luna_test(libluna/TestSharedPtr.cpp TestSharedPtr)
 luna_test(libc/TestScanf.cpp TestScanf)
 luna_test(libc/TestString.cpp TestString)
 luna_test(libc/TestEnv.cpp TestEnv)
+luna_test(libc/TestGlobalCtors.cpp TestGlobalCtors)
 
 luna_app(run-tests.cpp run-tests)
 endif()

tests/libc/TestGlobalCtors.cpp

@@ -0,0 +1,42 @@
+#include <stdio.h>
+#include <string.h>
+#include <test.h>
+#include <time.h>
+
+struct TestStruct
+{
+    TestStruct(const char* name) : m_name(name)
+    {
+        // Just to make sure this constructor doesn't get optimized out
+        time_t t = time(NULL);
+        ctime(&t);
+    }
+
+    const char* name()
+    {
+        return m_name;
+    }
+
+  private:
+    const char* m_name;
+};
+
+TestStruct g_struct("Example Struct");
+
+TestResult test_successful_global_constructor()
+{
+    validate(g_struct.name());
+
+    validate(!strcmp(g_struct.name(), "Example Struct"));
+
+    test_success;
+}
+
+Result<void> test_main()
+{
+    test_prelude;
+
+    run_test(test_successful_global_constructor);
+
+    return {};
+}

tools/setup-binutils.sh

@@ -39,7 +39,7 @@ unset CXX
 unset LD
 unset AR
 
-../binutils-$LUNA_BINUTILS_VERSION_REQUIRED/configure --prefix="$BUILD_PREFIX" --target=$BUILD_TARGET --disable-nls --with-sysroot=$BUILD_SYSROOT --disable-werror --enable-warn-rwx-segments=no
+../binutils-$LUNA_BINUTILS_VERSION_REQUIRED/configure --prefix="$BUILD_PREFIX" --target=$BUILD_TARGET --disable-nls --with-sysroot=$BUILD_SYSROOT --disable-werror --enable-warn-rwx-segments=no --enable-initfini-array
 
 echo Building Binutils...
 

tools/setup-gcc.sh

@@ -51,7 +51,7 @@ unset CXX
 unset LD
 unset AR
 
-../gcc-$LUNA_GCC_VERSION_REQUIRED/configure --prefix="$BUILD_PREFIX" --target=$BUILD_TARGET --disable-nls --with-sysroot=$BUILD_SYSROOT --enable-languages=c,c++
+../gcc-$LUNA_GCC_VERSION_REQUIRED/configure --prefix="$BUILD_PREFIX" --target=$BUILD_TARGET --disable-nls --with-sysroot=$BUILD_SYSROOT --enable-languages=c,c++ --enable-initfini-array
 
 echo Building GCC...