[libc-commits] [libc] [libc] Remove the optional arguments for NVPTX constructors (PR #69536)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/69536

Summary:
We call the global constructors by function pointer. For whatever reason
the NVPTX architecture relies very specifically on the arguments to the
functoin pointer invocation matching what the function is implemented
as. This is problembatic as most of these constructors are generated
with no arguments. This patch removes the extended arguments that GNU
and LLVM use for the constructors optionally so that it can support the
common case.


>From d81005f79354dd2f5f2ee3fe5e480162bec826b9 Mon Sep 17 00:00:00 2001
From: Joseph Huber <jhuber6 at vols.utk.edu>
Date: Wed, 18 Oct 2023 18:52:29 -0500
Subject: [PATCH] [libc] Remove the optional arguments for NVPTX constructors

Summary:
We call the global constructors by function pointer. For whatever reason
the NVPTX architecture relies very specifically on the arguments to the
functoin pointer invocation matching what the function is implemented
as. This is problembatic as most of these constructors are generated
with no arguments. This patch removes the extended arguments that GNU
and LLVM use for the constructors optionally so that it can support the
common case.
---
 libc/startup/gpu/nvptx/start.cpp                          | 8 +++++---
 .../test/integration/startup/gpu/init_fini_array_test.cpp | 4 ++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/libc/startup/gpu/nvptx/start.cpp b/libc/startup/gpu/nvptx/start.cpp
index 1ff187a577789f1..554c2ac385f0141 100644
--- a/libc/startup/gpu/nvptx/start.cpp
+++ b/libc/startup/gpu/nvptx/start.cpp
@@ -24,13 +24,15 @@ uintptr_t *__fini_array_start [[gnu::visibility("protected")]];
 uintptr_t *__fini_array_end [[gnu::visibility("protected")]];
 }
 
-using InitCallback = void(int, char **, char **);
+// Nvidia requires that the signature of the function pointers match. This means
+// we cannot support the extended constructor arguments.
+using InitCallback = void(void);
 using FiniCallback = void(void);
 
-static void call_init_array_callbacks(int argc, char **argv, char **env) {
+static void call_init_array_callbacks(int, char **, char **) {
   size_t init_array_size = __init_array_end - __init_array_start;
   for (size_t i = 0; i < init_array_size; ++i)
-    reinterpret_cast<InitCallback *>(__init_array_start[i])(argc, argv, env);
+    reinterpret_cast<InitCallback *>(__init_array_start[i])();
 }
 
 static void call_fini_array_callbacks() {
diff --git a/libc/test/integration/startup/gpu/init_fini_array_test.cpp b/libc/test/integration/startup/gpu/init_fini_array_test.cpp
index ead05f0240585a4..ceedd5fc813589c 100644
--- a/libc/test/integration/startup/gpu/init_fini_array_test.cpp
+++ b/libc/test/integration/startup/gpu/init_fini_array_test.cpp
@@ -37,11 +37,11 @@ A global(GLOBAL_INDEX, INITVAL_INITIALIZER);
 int initval = 0;
 int before = 0;
 
-__attribute__((constructor(101))) void run_before(int, char **, char **) {
+__attribute__((constructor(101))) void run_before() {
   before = BEFORE_INITIALIZER;
 }
 
-__attribute__((constructor(65535))) void run_after(int, char **, char **) {
+__attribute__((constructor(65535))) void run_after() {
   ASSERT_EQ(before, BEFORE_INITIALIZER);
 }