Commit 4c2ac61a authored by Keith Packard's avatar Keith Packard Committed by Johan Hedberg
Browse files

lib/libc: Provide optional check for time_t size 



The LIBC_ALLOW_LESS_THAN_64BIT_TIME option disables a compile-time check
ensuring that time_t can hold 64-bit values. This check can prevent
accidental builds on targets with 32-bit time_t and the consequent 2038
issues.

This option is enabled when using the native C library as i386 glibc
uses 32-bit time_t.

A new file, validate_libc.c, is added to lib/libc to contain this and any
future libc tests. The check for CONFIG_EXTERNAL_LIBC is moved to
libc/CMakeLists.txt to ensure that this new file is always compiled.

Signed-off-by: default avatarKeith Packard <keithp@keithp.com>
parent ff293bb6

lib/CMakeLists.txt

+0 −2
Original line number Diff line number Diff line
@@ -4,9 +4,7 @@ 
add_compile_options($<TARGET_PROPERTY:compiler,warning_shadow_variables>)



add_subdirectory(crc)

if(NOT CONFIG_EXTERNAL_LIBC)

add_subdirectory(libc)

endif()

if(NOT CONFIG_NATIVE_LIBC)

add_subdirectory(posix)

endif()

lib/libc/CMakeLists.txt

+18 −12
Original line number Diff line number Diff line 
# SPDX-License-Identifier: Apache-2.0



if(NOT CONFIG_EXTERNAL_LIBC)

  zephyr_syscall_header(

    ${ZEPHYR_BASE}/include/zephyr/sys/libc-hooks.h

    )
@@ -12,3 +13,8 @@ add_subdirectory_ifdef(CONFIG_NEWLIB_LIBC newlib) 
  add_subdirectory_ifdef(CONFIG_PICOLIBC          picolibc)



  add_subdirectory(common)

endif()



zephyr_sources(

  validate_libc.c

  )

lib/libc/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -18,6 +18,18 @@ config REQUIRES_FLOAT_PRINTF 
	  Select a printf implementation that provides a complete

	  implementation including floating point support.



config LIBC_ALLOW_LESS_THAN_64BIT_TIME

	bool "Don't require that time_t be at least 64-bits"

	default y if NATIVE_LIBC

	help

	  When selected, time_t will not be required to be at least 64

	  bits. Background: To avoid Y2038 issues time_t needs to be

	  bigger than 32bits. But some C libraries do not provide or

	  default to a type for time_t which is at least

	  64bits. Enable this option if your C library defined time_t

	  is more than 32bits (e.g. 48 bits) or are sure your project

	  is not subject to Y2038 issues.



config FULL_LIBC_SUPPORTED

	bool

	help

lib/libc/validate_libc.c

0 → 100644
+18 −0
Original line number Diff line number Diff line 
/*

 * Copyright © 2025 Keith Packard <keithp@keithp.com>

 *

 * SPDX-License-Identifier: Apache-2.0

 */



#include <zephyr/kernel.h>

#include <zephyr/toolchain.h>



/* Validate various C library implementation characteristics */



#ifndef CONFIG_LIBC_ALLOW_LESS_THAN_64BIT_TIME

#include <time.h>

/*

 * Ensure that time_t can hold at least 64 bit values.

 */

BUILD_ASSERT(sizeof(time_t) >= 8, "time_t cannot hold 64-bit values");

#endif

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