[libc-commits] [libc] POC: add snmalloc as an alternative allocator to libc (PR #122284)

Schrodinger ZHU Yifan via libc-commits libc-commits at lists.llvm.org
Wed Jan 15 22:16:28 PST 2025


https://github.com/SchrodingerZhu updated https://github.com/llvm/llvm-project/pull/122284

>From ddedf1e4b10a9b386fd334c3babcfd604bed6c62 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <i at zhuyi.fan>
Date: Thu, 9 Jan 2025 22:57:57 +0800
Subject: [PATCH 1/5] POC: add snmalloc as an alternative allocator to libc

---
 libc/src/stdlib/CMakeLists.txt             | 41 +++++++++++-
 libc/src/stdlib/snmalloc/CMakeLists.txt    | 75 ++++++++++++++++++++++
 libc/src/stdlib/snmalloc/aligned_alloc.cpp |  0
 libc/src/stdlib/snmalloc/calloc.cpp        |  0
 libc/src/stdlib/snmalloc/free.cpp          |  0
 libc/src/stdlib/snmalloc/malloc.cpp        |  9 +++
 libc/src/stdlib/snmalloc/mallopt.cpp       |  0
 libc/src/stdlib/snmalloc/realloc.cpp       |  0
 libc/src/stdlib/snmalloc/support.h         | 14 ++++
 9 files changed, 138 insertions(+), 1 deletion(-)
 create mode 100644 libc/src/stdlib/snmalloc/CMakeLists.txt
 create mode 100644 libc/src/stdlib/snmalloc/aligned_alloc.cpp
 create mode 100644 libc/src/stdlib/snmalloc/calloc.cpp
 create mode 100644 libc/src/stdlib/snmalloc/free.cpp
 create mode 100644 libc/src/stdlib/snmalloc/malloc.cpp
 create mode 100644 libc/src/stdlib/snmalloc/mallopt.cpp
 create mode 100644 libc/src/stdlib/snmalloc/realloc.cpp
 create mode 100644 libc/src/stdlib/snmalloc/support.h

diff --git a/libc/src/stdlib/CMakeLists.txt b/libc/src/stdlib/CMakeLists.txt
index 40ba9ead9a7ae6..7d0dfd1aa9da4b 100644
--- a/libc/src/stdlib/CMakeLists.txt
+++ b/libc/src/stdlib/CMakeLists.txt
@@ -324,7 +324,46 @@ add_entrypoint_object(
 )
 
 if(NOT LIBC_TARGET_OS_IS_BAREMETAL AND NOT LIBC_TARGET_OS_IS_GPU)
-  if(LLVM_LIBC_INCLUDE_SCUDO)
+  if (NOT "${LLVM_LIBC_INCLUDE_SNMALLOC}" STREQUAL "")
+    message(STATUS "Including snmalloc as the allocator, source directory: ${LLVM_LIBC_INCLUDE_SNMALLOC}")
+    add_subdirectory(snmalloc)
+    add_entrypoint_object(
+      malloc
+      ALIAS
+      DEPENDS
+        .snmalloc.malloc
+    )
+    add_entrypoint_object(
+      calloc
+      ALIAS
+      DEPENDS
+        .snmalloc.calloc
+    )
+    add_entrypoint_object(
+      realloc
+      ALIAS
+      DEPENDS
+        .snmalloc.realloc
+    )
+    add_entrypoint_object(
+      aligned_alloc
+      ALIAS
+      DEPENDS
+        .snmalloc.aligned_alloc
+    )
+    add_entrypoint_object(
+      free
+      ALIAS
+      DEPENDS
+        .snmalloc.free
+    )
+    add_entrypoint_object(
+      mallopt
+      ALIAS
+      DEPENDS
+        .snmalloc.mallopt
+    )
+  elseif(LLVM_LIBC_INCLUDE_SCUDO)
     set(SCUDO_DEPS "")
 
     include(${LIBC_SOURCE_DIR}/../compiler-rt/cmake/Modules/AllSupportedArchDefs.cmake)
diff --git a/libc/src/stdlib/snmalloc/CMakeLists.txt b/libc/src/stdlib/snmalloc/CMakeLists.txt
new file mode 100644
index 00000000000000..3971ea42db1744
--- /dev/null
+++ b/libc/src/stdlib/snmalloc/CMakeLists.txt
@@ -0,0 +1,75 @@
+set(SNMALLOC_USE_SELF_VENDORED_STL ON CACHE BOOL "use freestanding snmalloc setup" FORCE)
+set(SNMALLOC_BUILD_TESTING OFF CACHE BOOL "disable snmalloc tests" FORCE)
+set(SNMALLOC_HEADER_ONLY_LIBRARY ON CACHE BOOL "use snmalloc as header only library" FORCE)
+
+# Disable installation
+macro (install)
+endmacro ()
+
+add_subdirectory(${LLVM_LIBC_INCLUDE_SNMALLOC} ${CMAKE_CURRENT_BINARY_DIR}/snmalloc EXCLUDE_FROM_ALL)
+
+target_compile_options(
+  snmalloc 
+  INTERFACE 
+    -ffreestanding
+    -nostdinc 
+    -Wno-newline-eof 
+    -Wno-extra-semi
+    -Wno-unused-command-line-argument
+    -Wno-ctad-maybe-unsupported
+    # TODO: define this
+    -DSTDERR_FILENO=2
+    -include ${CMAKE_CURRENT_SOURCE_DIR}/support.h
+    # include_directories does not propagate, use options instead
+    -isystem ${COMPILER_RESOURCE_DIR}/include
+    -isystem ${LIBC_INCLUDE_DIR}
+)
+add_dependencies(snmalloc libc-headers)
+
+add_entrypoint_object(
+  malloc
+  SRCS
+    malloc.cpp
+  DEPENDS
+    snmalloc
+)
+
+add_entrypoint_object(
+  calloc
+  SRCS
+    calloc.cpp
+  DEPENDS
+    snmalloc
+)
+
+add_entrypoint_object(
+  realloc
+  SRCS
+    realloc.cpp
+  DEPENDS
+    snmalloc
+)
+
+add_entrypoint_object(
+  aligned_alloc
+  SRCS
+    aligned_alloc.cpp
+  DEPENDS
+    snmalloc
+)
+
+add_entrypoint_object(
+  free
+  SRCS
+    free.cpp
+  DEPENDS
+    snmalloc
+)
+
+add_entrypoint_object(
+  mallopt
+  SRCS
+    mallopt.cpp
+  DEPENDS
+    snmalloc
+)
diff --git a/libc/src/stdlib/snmalloc/aligned_alloc.cpp b/libc/src/stdlib/snmalloc/aligned_alloc.cpp
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/libc/src/stdlib/snmalloc/calloc.cpp b/libc/src/stdlib/snmalloc/calloc.cpp
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/libc/src/stdlib/snmalloc/free.cpp b/libc/src/stdlib/snmalloc/free.cpp
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/libc/src/stdlib/snmalloc/malloc.cpp b/libc/src/stdlib/snmalloc/malloc.cpp
new file mode 100644
index 00000000000000..644f2eef0ed2bf
--- /dev/null
+++ b/libc/src/stdlib/snmalloc/malloc.cpp
@@ -0,0 +1,9 @@
+#include "src/stdlib/malloc.h"
+#include "snmalloc/snmalloc.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+LLVM_LIBC_FUNCTION(void *, malloc, (size_t size)) {
+  return snmalloc::libc::malloc(size);
+}
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/snmalloc/mallopt.cpp b/libc/src/stdlib/snmalloc/mallopt.cpp
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/libc/src/stdlib/snmalloc/realloc.cpp b/libc/src/stdlib/snmalloc/realloc.cpp
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/libc/src/stdlib/snmalloc/support.h b/libc/src/stdlib/snmalloc/support.h
new file mode 100644
index 00000000000000..4909667c1a50d8
--- /dev/null
+++ b/libc/src/stdlib/snmalloc/support.h
@@ -0,0 +1,14 @@
+#include "src/sys/random/getrandom.h"
+
+// TODO: define this
+inline int getentropy(void *buf, size_t size) {
+  while (size > 0) {
+    ssize_t ret = LIBC_NAMESPACE::getrandom(buf, size, 0);
+    if (ret < 0) {
+      return -1;
+    }
+    buf = (char *)buf + ret;
+    size -= ret;
+  }
+  return 0;
+}

>From 96ebfa909efe6f6f31c6a28e99649a586f152404 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <i at zhuyi.fan>
Date: Thu, 16 Jan 2025 04:08:22 +0000
Subject: [PATCH 2/5] adjust build

---
 libc/src/stdlib/snmalloc/CMakeLists.txt |  2 +-
 libc/src/stdlib/snmalloc/free.cpp       | 17 +++++++++++++++++
 libc/src/stdlib/snmalloc/malloc.cpp     |  8 ++++++++
 libc/src/stdlib/snmalloc/support.h      | 14 --------------
 4 files changed, 26 insertions(+), 15 deletions(-)
 delete mode 100644 libc/src/stdlib/snmalloc/support.h

diff --git a/libc/src/stdlib/snmalloc/CMakeLists.txt b/libc/src/stdlib/snmalloc/CMakeLists.txt
index 3971ea42db1744..516505c09a13d1 100644
--- a/libc/src/stdlib/snmalloc/CMakeLists.txt
+++ b/libc/src/stdlib/snmalloc/CMakeLists.txt
@@ -19,7 +19,7 @@ target_compile_options(
     -Wno-ctad-maybe-unsupported
     # TODO: define this
     -DSTDERR_FILENO=2
-    -include ${CMAKE_CURRENT_SOURCE_DIR}/support.h
+    -DSNMALLOC_USE_PTHREAD_DESTRUCTORS
     # include_directories does not propagate, use options instead
     -isystem ${COMPILER_RESOURCE_DIR}/include
     -isystem ${LIBC_INCLUDE_DIR}
diff --git a/libc/src/stdlib/snmalloc/free.cpp b/libc/src/stdlib/snmalloc/free.cpp
index e69de29bb2d1d6..a3160c15d0df38 100644
--- a/libc/src/stdlib/snmalloc/free.cpp
+++ b/libc/src/stdlib/snmalloc/free.cpp
@@ -0,0 +1,17 @@
+//===-- Implementation of free --------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/free.h"
+#include "snmalloc/snmalloc.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+LLVM_LIBC_FUNCTION(void, free, (void * ptr)) {
+  return snmalloc::libc::free(ptr);
+}
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/snmalloc/malloc.cpp b/libc/src/stdlib/snmalloc/malloc.cpp
index 644f2eef0ed2bf..ab58e63743016a 100644
--- a/libc/src/stdlib/snmalloc/malloc.cpp
+++ b/libc/src/stdlib/snmalloc/malloc.cpp
@@ -1,3 +1,11 @@
+//===-- Implementation of malloc ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
 #include "src/stdlib/malloc.h"
 #include "snmalloc/snmalloc.h"
 #include "src/__support/common.h"
diff --git a/libc/src/stdlib/snmalloc/support.h b/libc/src/stdlib/snmalloc/support.h
deleted file mode 100644
index 4909667c1a50d8..00000000000000
--- a/libc/src/stdlib/snmalloc/support.h
+++ /dev/null
@@ -1,14 +0,0 @@
-#include "src/sys/random/getrandom.h"
-
-// TODO: define this
-inline int getentropy(void *buf, size_t size) {
-  while (size > 0) {
-    ssize_t ret = LIBC_NAMESPACE::getrandom(buf, size, 0);
-    if (ret < 0) {
-      return -1;
-    }
-    buf = (char *)buf + ret;
-    size -= ret;
-  }
-  return 0;
-}

>From bc6eb843e3cff098a20adde7f408d8a7d38e9915 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <i at zhuyi.fan>
Date: Thu, 16 Jan 2025 04:26:12 +0000
Subject: [PATCH 3/5] implement all symbols

---
 libc/src/stdlib/snmalloc/aligned_alloc.cpp | 17 +++++++++++++++++
 libc/src/stdlib/snmalloc/calloc.cpp        | 17 +++++++++++++++++
 libc/src/stdlib/snmalloc/free.cpp          |  2 +-
 libc/src/stdlib/snmalloc/mallopt.cpp       | 13 +++++++++++++
 libc/src/stdlib/snmalloc/realloc.cpp       | 17 +++++++++++++++++
 5 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/libc/src/stdlib/snmalloc/aligned_alloc.cpp b/libc/src/stdlib/snmalloc/aligned_alloc.cpp
index e69de29bb2d1d6..ee1d74ca9c778c 100644
--- a/libc/src/stdlib/snmalloc/aligned_alloc.cpp
+++ b/libc/src/stdlib/snmalloc/aligned_alloc.cpp
@@ -0,0 +1,17 @@
+//===-- Implementation of aligned_alloc -----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/aligned_alloc.h"
+#include "snmalloc/snmalloc.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+LLVM_LIBC_FUNCTION(void *, aligned_alloc, (size_t alignment, size_t size)) {
+  return snmalloc::libc::aligned_alloc(alignment, size);
+}
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/snmalloc/calloc.cpp b/libc/src/stdlib/snmalloc/calloc.cpp
index e69de29bb2d1d6..39af67607bf709 100644
--- a/libc/src/stdlib/snmalloc/calloc.cpp
+++ b/libc/src/stdlib/snmalloc/calloc.cpp
@@ -0,0 +1,17 @@
+//===-- Implementation of calloc ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/calloc.h"
+#include "snmalloc/snmalloc.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+LLVM_LIBC_FUNCTION(void *, calloc, (size_t num, size_t size)) {
+  return snmalloc::libc::calloc(num, size);
+}
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/snmalloc/free.cpp b/libc/src/stdlib/snmalloc/free.cpp
index a3160c15d0df38..eb403710fffada 100644
--- a/libc/src/stdlib/snmalloc/free.cpp
+++ b/libc/src/stdlib/snmalloc/free.cpp
@@ -11,7 +11,7 @@
 #include "src/__support/common.h"
 
 namespace LIBC_NAMESPACE_DECL {
-LLVM_LIBC_FUNCTION(void, free, (void * ptr)) {
+LLVM_LIBC_FUNCTION(void, free, (void *ptr)) {
   return snmalloc::libc::free(ptr);
 }
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/snmalloc/mallopt.cpp b/libc/src/stdlib/snmalloc/mallopt.cpp
index e69de29bb2d1d6..c52d68e3d52230 100644
--- a/libc/src/stdlib/snmalloc/mallopt.cpp
+++ b/libc/src/stdlib/snmalloc/mallopt.cpp
@@ -0,0 +1,13 @@
+//===-- Implementation of mallopt stub ------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+LLVM_LIBC_FUNCTION(int, mallopt, (int, int)) { return 0; }
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/snmalloc/realloc.cpp b/libc/src/stdlib/snmalloc/realloc.cpp
index e69de29bb2d1d6..36972e0a2232ec 100644
--- a/libc/src/stdlib/snmalloc/realloc.cpp
+++ b/libc/src/stdlib/snmalloc/realloc.cpp
@@ -0,0 +1,17 @@
+//===-- Implementation of realloc -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/realloc.h"
+#include "snmalloc/snmalloc.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+LLVM_LIBC_FUNCTION(void *, realloc, (void *ptr, size_t size)) {
+  return snmalloc::libc::realloc(ptr, size);
+}
+} // namespace LIBC_NAMESPACE_DECL

>From 5f6651d0c0a8d7cfc270bca198cc5db9b09c8f45 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <i at zhuyi.fan>
Date: Thu, 16 Jan 2025 05:09:37 +0000
Subject: [PATCH 4/5] setup dependencies

---
 libc/src/stdlib/snmalloc/CMakeLists.txt | 43 +++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/libc/src/stdlib/snmalloc/CMakeLists.txt b/libc/src/stdlib/snmalloc/CMakeLists.txt
index 516505c09a13d1..cc7172c947c4c2 100644
--- a/libc/src/stdlib/snmalloc/CMakeLists.txt
+++ b/libc/src/stdlib/snmalloc/CMakeLists.txt
@@ -24,8 +24,46 @@ target_compile_options(
     -isystem ${COMPILER_RESOURCE_DIR}/include
     -isystem ${LIBC_INCLUDE_DIR}
 )
+
 add_dependencies(snmalloc libc-headers)
 
+set(SNMALLOC_DEPS
+  # includes
+  libc.include.errno
+  libc.include.fcntl
+  libc.include.limits
+  libc.include.pthread
+  libc.include.stdio
+  libc.include.stdint
+  libc.include.stdlib
+  libc.include.string
+  libc.include.strings
+  libc.include.sys_mman
+  libc.include.sys_prctl
+  libc.include.sys_random
+  libc.include.sys_syscall
+  libc.include.sys_uio
+  libc.include.unistd
+  # symbols
+  libc.src.errno.errno
+  libc.src.fcntl.open
+  libc.src.pthread.pthread_key_create
+  libc.src.pthread.pthread_setspecific
+  libc.src.stdlib.abort
+  libc.src.stdlib.atexit
+  libc.src.string.memset
+  libc.src.string.strlen
+  libc.src.sys.mman.madvise
+  libc.src.sys.mman.mmap
+  libc.src.sys.uio.writev
+  libc.src.time.clock_gettime
+  libc.src.unistd.__llvm_libc_syscall
+  libc.src.unistd.close
+  libc.src.unistd.fsync
+  libc.src.unistd.getentropy
+  libc.src.unistd.read
+)
+
 add_entrypoint_object(
   malloc
   SRCS
@@ -40,6 +78,7 @@ add_entrypoint_object(
     calloc.cpp
   DEPENDS
     snmalloc
+    ${SNMALLOC_DEPS}
 )
 
 add_entrypoint_object(
@@ -48,6 +87,7 @@ add_entrypoint_object(
     realloc.cpp
   DEPENDS
     snmalloc
+    ${SNMALLOC_DEPS}
 )
 
 add_entrypoint_object(
@@ -56,6 +96,7 @@ add_entrypoint_object(
     aligned_alloc.cpp
   DEPENDS
     snmalloc
+    ${SNMALLOC_DEPS}
 )
 
 add_entrypoint_object(
@@ -64,6 +105,7 @@ add_entrypoint_object(
     free.cpp
   DEPENDS
     snmalloc
+    ${SNMALLOC_DEPS}
 )
 
 add_entrypoint_object(
@@ -72,4 +114,5 @@ add_entrypoint_object(
     mallopt.cpp
   DEPENDS
     snmalloc
+    ${SNMALLOC_DEPS}
 )

>From 1382389b1f693f98f9b253ef53ee6a8985350899 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <i at zhuyi.fan>
Date: Thu, 16 Jan 2025 06:12:42 +0000
Subject: [PATCH 5/5] make hermetic build pass with snmalloc

---
 libc/src/stdlib/snmalloc/CMakeLists.txt |  1 +
 libc/src/stdlib/snmalloc/override.h     | 32 +++++++++++++++++++++++++
 libc/test/src/stdlib/CMakeLists.txt     |  4 +++-
 3 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 libc/src/stdlib/snmalloc/override.h

diff --git a/libc/src/stdlib/snmalloc/CMakeLists.txt b/libc/src/stdlib/snmalloc/CMakeLists.txt
index cc7172c947c4c2..e360b36f5fb3ad 100644
--- a/libc/src/stdlib/snmalloc/CMakeLists.txt
+++ b/libc/src/stdlib/snmalloc/CMakeLists.txt
@@ -21,6 +21,7 @@ target_compile_options(
     -DSTDERR_FILENO=2
     -DSNMALLOC_USE_PTHREAD_DESTRUCTORS
     # include_directories does not propagate, use options instead
+    -include ${CMAKE_CURRENT_SOURCE_DIR}/override.h
     -isystem ${COMPILER_RESOURCE_DIR}/include
     -isystem ${LIBC_INCLUDE_DIR}
 )
diff --git a/libc/src/stdlib/snmalloc/override.h b/libc/src/stdlib/snmalloc/override.h
new file mode 100644
index 00000000000000..a36a6316790fbd
--- /dev/null
+++ b/libc/src/stdlib/snmalloc/override.h
@@ -0,0 +1,32 @@
+//===-- Macro Override for SnMalloc ---------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// skip special headers
+#define LLVM_LIBC_COMMON_H
+#define LLVM_LIBC_ERRNO_H
+
+// define common macros
+#define __BEGIN_C_DECLS namespace LIBC_NAMESPACE {
+#define __END_C_DECLS                                                          \
+  }                                                                            \
+  using namespace LIBC_NAMESPACE;
+
+#define _Noreturn [[noreturn]]
+#define _Alignas alignas
+#define _Static_assert static_assert
+#define _Alignof alignof
+#define _Thread_local thread_local
+
+// Use empty definition to avoid spec mismatching
+// We are building internally anyway, hence noexcept does not matter here
+#define __NOEXCEPT
+
+// Enforce internal errno implementation
+#include "hdr/errno_macros.h"
+#include "src/errno/libc_errno.h"
+#define errno libc_errno
diff --git a/libc/test/src/stdlib/CMakeLists.txt b/libc/test/src/stdlib/CMakeLists.txt
index 8cc0428632ba39..2346a8bae08f87 100644
--- a/libc/test/src/stdlib/CMakeLists.txt
+++ b/libc/test/src/stdlib/CMakeLists.txt
@@ -420,7 +420,9 @@ if(LLVM_LIBC_FULL_BUILD)
   )
 
   # Only baremetal and GPU has an in-tree 'malloc' implementation.
-  if(LIBC_TARGET_OS_IS_BAREMETAL OR LIBC_TARGET_OS_IS_GPU)
+  if(LIBC_TARGET_OS_IS_BAREMETAL
+      OR LIBC_TARGET_OS_IS_GPU
+      OR NOT "${LLVM_LIBC_INCLUDE_SNMALLOC}" STREQUAL "")
     add_libc_test(
       malloc_test
       HERMETIC_TEST_ONLY



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