From cf060b6bf28fff62fd38a1c44f377d389e763f7b Mon Sep 17 00:00:00 2001
From: chao an <anchao@lixiang.com>
Date: Tue, 10 Dec 2024 12:45:49 +0800
Subject: [PATCH] libs/libc: add a option to disable path buffer by default

If the current platform does not require a large PATH_MAX size support and toolchain supports alloca(),
we could turn off this option to improve performance.

Signed-off-by: chao an <anchao@lixiang.com>
---
 include/nuttx/lib/lib.h       |  8 ++++++++
 libs/libc/misc/CMakeLists.txt |  7 +++++--
 libs/libc/misc/Kconfig        | 12 ++++++++++++
 libs/libc/misc/Make.defs      |  6 +++++-
 4 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/include/nuttx/lib/lib.h b/include/nuttx/lib/lib.h
index 9593d9bd74..3b65e98eb8 100644
--- a/include/nuttx/lib/lib.h
+++ b/include/nuttx/lib/lib.h
@@ -31,6 +31,9 @@
 #include <nuttx/fs/fs.h>
 #include <nuttx/kmalloc.h>
 
+#include <limits.h>
+#include <alloca.h>
+
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
@@ -119,8 +122,13 @@ unsigned long nrand(unsigned long limit);
 
 /* Functions defined in lib_pathbuffer.c ************************************/
 
+#ifdef CONFIG_LIBC_PATHBUFFER
 FAR char *lib_get_pathbuffer(void);
 void lib_put_pathbuffer(FAR char *buffer);
+#else
+#  define lib_get_pathbuffer() alloca(PATH_MAX)
+#  define lib_put_pathbuffer(b)
+#endif
 
 /* Functions defined in lib_realpath.c **************************************/
 
diff --git a/libs/libc/misc/CMakeLists.txt b/libs/libc/misc/CMakeLists.txt
index 39b4d86ecb..6c4a5cd09f 100644
--- a/libs/libc/misc/CMakeLists.txt
+++ b/libs/libc/misc/CMakeLists.txt
@@ -47,8 +47,11 @@ list(
   lib_mkdirat.c
   lib_utimensat.c
   lib_mallopt.c
-  lib_getnprocs.c
-  lib_pathbuffer.c)
+  lib_getnprocs.c)
+
+if(CONFIG_LIBC_PATHBUFFER)
+  list(APPEND SRCS lib_pathbuffer.c)
+endif()
 
 # Support for platforms that do not have long long types
 
diff --git a/libs/libc/misc/Kconfig b/libs/libc/misc/Kconfig
index d834ca0c63..44d66689d6 100644
--- a/libs/libc/misc/Kconfig
+++ b/libs/libc/misc/Kconfig
@@ -119,6 +119,16 @@ config LIBC_MEM_FD_VFS_PATH
 	---help---
 		The relative path to where memfd will exist in the tmpfs namespace.
 
+config LIBC_PATHBUFFER
+	bool "Enable global path buffer"
+	default !DEFAULT_SMALL
+	---help---
+		Enable this option to enable the global path buffer, otherwise use stack variables via alloca().
+		If the current platform does not require a large PATH_MAX size support and toolchain supports alloca(),
+		we could turn off this option to improve performance.
+
+if LIBC_PATHBUFFER
+
 config LIBC_MAX_PATHBUFFER
 	int "Maximum size of a temporary file path buffer array"
 	range 0 32
@@ -133,6 +143,8 @@ config LIBC_PATHBUFFER_MALLOC
 	---help---
 		Enable malloc path buffer from the heap when pathbuffer is insufficient.
 
+endif # LIBC_PATHBUFFER
+
 config LIBC_BACKTRACE_BUFFSIZE
 	int "The size of backtrace record buffer"
 	depends on SCHED_BACKTRACE
diff --git a/libs/libc/misc/Make.defs b/libs/libc/misc/Make.defs
index a3c22278a7..ae93069639 100644
--- a/libs/libc/misc/Make.defs
+++ b/libs/libc/misc/Make.defs
@@ -27,7 +27,11 @@ CSRCS += lib_getrandom.c lib_xorshift128.c lib_tea_encrypt.c lib_tea_decrypt.c
 CSRCS += lib_cxx_initialize.c lib_impure.c lib_memfd.c lib_mutex.c
 CSRCS += lib_fchmodat.c lib_fstatat.c lib_getfullpath.c lib_openat.c
 CSRCS += lib_mkdirat.c lib_utimensat.c lib_mallopt.c
-CSRCS += lib_idr.c lib_getnprocs.c lib_pathbuffer.c
+CSRCS += lib_idr.c lib_getnprocs.c
+
+ifeq ($(CONFIG_LIBC_PATHBUFFER),y)
+CSRCS += lib_pathbuffer.c
+endif
 
 # Support for platforms that do not have long long types