compilation error when using MBEDTLS_PLATFORM_CALLOC_MACRO and MBEDTLS_PLATFORM_C

[RonEld]

Description

• Type: Bug
• Priority: Minor

Rasied by Eric Tung by Email

---

Bug

OS
linux|windows|

mbed TLS build:
Version: development branch
Configuration: define MBEDTLS_PLATFORM_CALLOC_MACRO, MBEDTLS_PLATFORM_FREE_MACRO and MBEDTLS_PLATFORM_C

Expected behavior
compilation to succeed
Actual behavior
compilation error:
Windows:

1>mbedtls\library\platform.c(54): error C2365: 'calloc' : redefinition; previous definition was 'function'
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\stdlib.h(598) : see declaration of 'calloc'
1>mbedtls\library\platform.c(55): error C2365: 'free' : redefinition; previous definition was 'function'
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\stdlib.h(599) : see declaration of 'free'
1>mbedtls\library\platform.c(60): error C2106: '=' : left operand must be l-value
1>mbedtls\library\platform.c(60): warning C4550: expression evaluates to a function which is missing an argument list
1>mbedtls\library\platform.c(61): error C2106: '=' : left operand must be l-value
1>mbedtls\library\platform.c(61): warning C4550: expression evaluates to a function which is missing an argument list

Linux:

In file included from platform.c:23:0:
../include/mbedtls/config.h:2784:39: error: \u2018calloc\u2019 redeclared as different kind of symbol
 #define MBEDTLS_PLATFORM_CALLOC_MACRO calloc
                                       ^
../include/mbedtls/platform.h:120:28: note: in expansion of macro \u2018MBEDTLS_PLATFORM_CALLOC_MACRO\u2019
 #define mbedtls_calloc     MBEDTLS_PLATFORM_CALLOC_MACRO
                            ^
platform.c:54:10: note: in expansion of macro \u2018mbedtls_calloc\u2019
 void * (*mbedtls_calloc)( size_t, size_t ) = MBEDTLS_PLATFORM_STD_CALLOC;
          ^
In file included from ../include/mbedtls/platform.h:60:0,
                 from platform.c:30:
/usr/include/stdlib.h:468:14: note: previous declaration of \u2018calloc\u2019 was here
 extern void *calloc (size_t __nmemb, size_t __size)
              ^
In file included from platform.c:30:0:
../include/mbedtls/platform.h:76:39: error: initializer element is not constant
 #define MBEDTLS_PLATFORM_STD_CALLOC   calloc /**< The default \c calloc function to use. */
                                       ^
platform.c:54:46: note: in expansion of macro \u2018MBEDTLS_PLATFORM_STD_CALLOC\u2019
 void * (*mbedtls_calloc)( size_t, size_t ) = MBEDTLS_PLATFORM_STD_CALLOC;
                                              ^
In file included from platform.c:23:0:
../include/mbedtls/config.h:2785:37: error: \u2018free\u2019 redeclared as different kind of symbol
 #define MBEDTLS_PLATFORM_FREE_MACRO free
                                     ^
../include/mbedtls/platform.h:119:28: note: in expansion of macro \u2018MBEDTLS_PLATFORM_FREE_MACRO\u2019
 #define mbedtls_free       MBEDTLS_PLATFORM_FREE_MACRO
                            ^
platform.c:55:8: note: in expansion of macro \u2018mbedtls_free\u2019
 void (*mbedtls_free)( void * )     = MBEDTLS_PLATFORM_STD_FREE;
        ^
In file included from ../include/mbedtls/platform.h:60:0,
                 from platform.c:30:
/usr/include/stdlib.h:483:13: note: previous declaration of \u2018free\u2019 was here
 extern void free (void *__ptr) __THROW;
             ^
In file included from platform.c:30:0:
../include/mbedtls/platform.h:79:41: error: initializer element is not constant
 #define MBEDTLS_PLATFORM_STD_FREE       free /**< The default \c free function to use. */
                                         ^
platform.c:55:38: note: in expansion of macro \u2018MBEDTLS_PLATFORM_STD_FREE\u2019
 void (*mbedtls_free)( void * )     = MBEDTLS_PLATFORM_STD_FREE;

Steps to reproduce
define MBEDTLS_PLATFORM_CALLOC_MACRO and MBEDTLS_PLATFORM_CALLOC_MACRO as the default macros.

*Although this is not the regular use, as platform calloc and free should be used when no platform calloc \ free are available, there shouldn't be a compilation error, or at least update documentation accordingly

[ciarmcom]

ARM Internal Ref: IOTSSL-2312

[hanno-becker]

Where does

 void * (*mbedtls_calloc)( size_t, size_t ) = MBEDTLS_PLATFORM_STD_CALLOC;

come from? It says it's platform.c L54 but this line instead is:

static void * (*mbedtls_calloc_func)( size_t, size_t ) = MBEDTLS_PLATFORM_STD_CALLOC;

@RonEld Can you clarify and show how to reproduce this? The current steps to reproduce have a typo, and I cannot guess what was originally meant.

[upbeat27]

@hanno-arm, I'm not OP but I have run into the same issue. Also,

 void * (*mbedtls_calloc)( size_t, size_t ) = MBEDTLS_PLATFORM_STD_CALLOC;

is from an older version of mbedtls.

The problem is this:
In order to use MBEDTLS_PLATFORM_FREE_MACRO and MBEDTLS_PLATFORM_CALLOC_MACRO one must define MBEDTLS_PLATFORM_MEMORY and MBEDTLS_PLATFORM_C as required by check_config.h:

#if defined(MBEDTLS_PLATFORM_FREE_MACRO) &&\
    ( !defined(MBEDTLS_PLATFORM_C) || !defined(MBEDTLS_PLATFORM_MEMORY) )
#error "MBEDTLS_PLATFORM_FREE_MACRO defined, but not all prerequisites"
#endif

#if defined(MBEDTLS_PLATFORM_CALLOC_MACRO) &&\
    ( !defined(MBEDTLS_PLATFORM_C) || !defined(MBEDTLS_PLATFORM_MEMORY) )
#error "MBEDTLS_PLATFORM_CALLOC_MACRO defined, but not all prerequisites"
#endif

So if you do this, in platform.h this does what you expect:

#define mbedtls_free       MBEDTLS_PLATFORM_FREE_MACRO
#define mbedtls_calloc     MBEDTLS_PLATFORM_CALLOC_MACRO

But in platform.c, you do not get what you expect:

static void * (*mbedtls_calloc_func)( size_t, size_t ) = MBEDTLS_PLATFORM_STD_CALLOC;
static void (*mbedtls_free_func)( void * ) = MBEDTLS_PLATFORM_STD_FREE;

void * mbedtls_calloc( size_t nmemb, size_t size )
{
    return (*mbedtls_calloc_func)( nmemb, size );
}

void mbedtls_free( void * ptr )
{
    (*mbedtls_free_func)( ptr );
}

int mbedtls_platform_set_calloc_free( void * (*calloc_func)( size_t, size_t ),
                              void (*free_func)( void * ) )
{
    mbedtls_calloc_func = calloc_func;
    mbedtls_free_func = free_func;
    return( 0 );
}

and therein lies the conflict. You get a macro, yet the functions are still there, you get previous declaration errors and redeclared errors.

So the steps to reproduce are try to use MBEDTLS_PLATFORM_FREE_MACRO and MBEDTLS_PLATFORM_CALLOC_MACRO, there is no combination of configuration options which will allow them to be used, unless I am missing something. If I am missing something let me know, because I can't seem to place what it is!

[hanno-becker]

@upbeat27 Thanks for the detailed information and for pointing out the recent code change. In fact, the line in question was changed in 7decfe8, but I think the issue is agnostic to that.

@upbeat27 @RonEld It seems that the code in platform.c that @upbeat27 quotes above should be guarded by !( defined(MBEDTLS_PLATFORM_FREE_MACRO) && defined(MBEDTLS_PLATFORM_CALLOC_MACRO) ). If these macros are defined, there's no need for mbedtls_calloc, mbedtls_free, mbedtls_platform_set_calloc_free(), and platform.h indeed makes no mention of them. Actually, if I try to compile with MBEDTLS_PLATFORM_{FREE/CALLOC}_MACRO defined, I get the compiler error error: no previous prototype for ‘mbedtls_platform_set_calloc_free’ reflecting that. The documentation is also clear on that:

/*
* By default mbed TLS uses the system-provided calloc() and free().
 * This allows different allocators (self-implemented or provided) to be
 * provided to the platform abstraction layer.
 *
 * Enabling MBEDTLS_PLATFORM_MEMORY without the
 * MBEDTLS_PLATFORM_{FREE,CALLOC}_MACROs will provide
 * "mbedtls_platform_set_calloc_free()" allowing you to set an alternative calloc() and
 * free() function pointer at runtime.
 *
 * Enabling MBEDTLS_PLATFORM_MEMORY and specifying
 * MBEDTLS_PLATFORM_{CALLOC,FREE}_MACROs will allow you to specify the
 * alternate function at compile time.
*/

I will create a PR guarding the mentioned code in platform.c.

[RonEld]

Closing this issue, as the OP, @dhhome2006 submitted the same issue in #1706