From 9c14c09962c43f11bb4eb4538904f81386f16b15 Mon Sep 17 00:00:00 2001
From: Calvin Rose <calsrose@gmail.com>
Date: Sun, 28 Jan 2024 15:53:41 -0600
Subject: [PATCH] Add explicit stdatomic config setting for #1374

There was some hacky workaround code for development versions of TCC
that interfered with other compilers and technically was not legal
c99.
---
 src/conf/janetconf.h |  1 +
 src/core/abstract.c  |  2 --
 src/core/capi.c      | 13 +++++++++++++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/conf/janetconf.h b/src/conf/janetconf.h
index 7110e5c3..66177838 100644
--- a/src/conf/janetconf.h
+++ b/src/conf/janetconf.h
@@ -54,6 +54,7 @@
 /* #define JANET_NO_INTERPRETER_INTERRUPT */
 /* #define JANET_NO_IPV6 */
 /* #define JANET_NO_CRYPTORAND */
+/* #define JANET_USE_STDATOMIC */
 
 /* Custom vm allocator support */
 /* #include <mimalloc.h> */
diff --git a/src/core/abstract.c b/src/core/abstract.c
index 407e9ced..5c0631b1 100644
--- a/src/core/abstract.c
+++ b/src/core/abstract.c
@@ -31,8 +31,6 @@
 #ifdef JANET_EV
 #ifdef JANET_WINDOWS
 #include <windows.h>
-#else
-#include <stdatomic.h>
 #endif
 #endif
 
diff --git a/src/core/capi.c b/src/core/capi.c
index 0f82910b..166f2c5e 100644
--- a/src/core/capi.c
+++ b/src/core/capi.c
@@ -35,6 +35,13 @@
 #endif
 #endif
 
+#ifdef JANET_USE_STDATOMIC
+#include <stdatomic.h>
+/* We don't need stdatomic on most compilers since we use compiler builtins for atomic operations.
+ * Some (TCC), explicitly require using stdatomic.h and don't have any exposed builtins (that I know of).
+ * For TCC and similar compilers, one would need -std=c11 or similar then to get access. */
+#endif
+
 JANET_NO_RETURN static void janet_top_level_signal(const char *msg) {
 #ifdef JANET_TOP_LEVEL_SIGNAL
     JANET_TOP_LEVEL_SIGNAL(msg);
@@ -496,6 +503,8 @@ void *janet_optabstract(const Janet *argv, int32_t argc, int32_t n, const JanetA
 JanetAtomicInt janet_atomic_inc(JanetAtomicInt volatile *x) {
 #ifdef JANET_WINDOWS
     return InterlockedIncrement(x);
+#elif defined(JANET_USE_STDATOMIC)
+    return atomic_fetch_add_explicit(x, 1, memory_order_relaxed) + 1;
 #else
     return __atomic_add_fetch(x, 1, __ATOMIC_RELAXED);
 #endif
@@ -504,6 +513,8 @@ JanetAtomicInt janet_atomic_inc(JanetAtomicInt volatile *x) {
 JanetAtomicInt janet_atomic_dec(JanetAtomicInt volatile *x) {
 #ifdef JANET_WINDOWS
     return InterlockedDecrement(x);
+#elif defined(JANET_USE_STDATOMIC)
+    return atomic_fetch_add_explicit(x, -1, memory_order_acq_rel) - 1;
 #else
     return __atomic_add_fetch(x, -1, __ATOMIC_ACQ_REL);
 #endif
@@ -512,6 +523,8 @@ JanetAtomicInt janet_atomic_dec(JanetAtomicInt volatile *x) {
 JanetAtomicInt janet_atomic_load(JanetAtomicInt volatile *x) {
 #ifdef JANET_WINDOWS
     return InterlockedOr(x, 0);
+#elif defined(JANET_USE_STDATOMIC)
+    return atomic_load_explicit(x, memory_order_acquire);
 #else
     return __atomic_load_n(x, __ATOMIC_ACQUIRE);
 #endif