Home | Manual | Playground

Cake - C23 and Beyond

Intro

Cake works as an extension for MSVC on Windows and as an extension for GCC on Linux. This approach makes Cake useful in real and existing programs.

When applicable, Cake uses the same command line options of MSVC and GCC.

Static analyzer

For static analyzer concepts of ownership and nullable pointers visit ownership

Include directories

On Windows, Cake can be used on the command line similarly to MSVC. Cake reads the INCLUDE variable, the same variable used by MSVC to locate the include directories.

Additionally, you can run Cake outside the Visual Studio command prompt by placing the file cakeconfig.h in the same directory or above the source files, and specifying the directories using #pragma dir.

If Cake doesn't find cakeconfig.h in the local directories, it will try to locate it in the same path as the Cake executable.

The -autoconfig option generates the cakeconfig.h automatically on both Windows and Linux.

On Windows, to manually discover which directories are included, you can run the command:

echo %INCLUDE%

at Visual Studio command prompt.

To find out what are the directories used by GCC type:

echo | gcc -E -Wp,-v -

Sample of cakeconfig.h


#ifdef __linux__
/*
   To find the include directories used my GCC type:   
   echo | gcc -E -Wp,-v -
*/
#pragma dir "/usr/lib/gcc/x86_64-linux-gnu/11/include"
#pragma dir "/usr/local/include"
#pragma dir "/usr/include/x86_64-linux-gnu"
#pragma dir "/usr/include"

#endif

#ifdef _WIN32
/*
   To find the include directories used my  MSVC,
   open Visual Studio Developer Commmand prompt and type:
   echo %INCLUDE%.
   Running Cake inside mscv command prompt uses %INCLUDE% automatically.
*/
#pragma dir "C:/Program Files/Microsoft Visual Studio/2022/Professional/VC/Tools/MSVC/14.38.33130/include"
#pragma dir "C:/Program Files/Microsoft Visual Studio/2022/Professional/VC/Tools/MSVC/14.38.33130/ATLMFC/include"
#pragma dir "C:/Program Files/Microsoft Visual Studio/2022/Professional/VC/Auxiliary/VS/include"
#pragma dir "C:/Program Files (x86)/Windows Kits/10/include/10.0.22000.0/ucrt"
#pragma dir "C:/Program Files (x86)/Windows Kits/10/include/10.0.22000.0/um"
#pragma dir "C:/Program Files (x86)/Windows Kits/10/include/10.0.22000.0/shared"
#pragma dir "C:/Program Files (x86)/Windows Kits/10/include/10.0.22000.0/winrt"
#pragma dir "C:/Program Files (x86)/Windows Kits/10/include/10.0.22000.0/cppwinrt"
#pragma dir "C:/Program Files (x86)/Windows Kits/NETFXSDK/4.8/include/um"

#endif

Sample, project cakeconfig.h


//system includes...etc
#include "C:\Program Files (x86)\cake\cakeconfig.h"

//project extra includes
#pragma dir ".\openssl\include"

Command line

cake [options] source1.c source2.c ...

SAMPLES

    cake source.c
    Compiles source.c and outputs /out/source.c

    cake -target=C11 source.c
    Compiles source.c and outputs C11 code at /out/source.c

cake file.c -o file.cc && cl file.cc
    Compiles file.c and outputs file.cc then use cl to compile file.cc

cake file.c -direct-compilation -o file.cc && cl file.cc
    Compiles file.c and outputs file.cc for direct compilation then use cl to compile file.cc

OPTIONS

-I (same as GCC and MSVC)

Adds a directory to the list of directories searched for include files

-no-output

Cake will not generate output

-D (same as GCC and MSVC)

Defines a preprocessing symbol for a source file

-E (same as GCC and MSVC)

Copies preprocessor output to standard output

-o name.c (same as GCC and MSVC)

Defines the output name, when we compile a single file

-dump-tokens

Output tokens before preprocessor

-Wname -Wno-name (same as GCC)

Enables or disable warnings. See warnings

-disable-assert

disable cake extension where assert is an statement. See extensions

-H (same as gcc, /showIncludes in MSVC)

Causes the compiler to output a list of the include files.

-preprocess-def-macro

preprocess def macros after expansion

-Wall

Enables all warnings

-sarif

Generates sarif files. Sarif Visual Studio plugin https://marketplace.visualstudio.com/items?itemName=WDGIS.MicrosoftSarifViewer

-sarif-path

Specifies the Sarif output dir.

Inside "Visual Studio -> External Tools" this command can be used for static analysis.

`-Wstyle -msvc-output -no-output -sarif -sarif-path "$(SolutionDir).sarif" $(ItemPath)´

-target=x86x64gcc, -target=x64msvc, -target=x64msvc

This is used for cross compiling.

-msvc-output

Output is compatible with Visual Studio IDE. (We can click on the error message and IDE selects the line.)

-fanalyzer

This option enables an static analysis of program flow. This is required for some ownership checks

-auto-config

Generates cakeconfig.h header.

On Windows, it must be generated inside the Visual Studio Command Prompt to read the INCLUDE variable. On Linux, it calls GCC with echo | gcc -v -E - 2>&1 and reads the output.

Output

The current backend generates C89-compatible code, which can be pipelined with existing compilers to produce executables.

The output is a simplified version of C89. It does not include the following features:

The goal is for this simplified version to function as an intermediate language (IL).

One directory called out is created keeping the same directory structure of the input files.

For instance:

cake c:\project\file1.c

output:

  c:\project
  ├── file1.c
  ├── out
      ├── file1.c

More files..

cake c:\project\file1.c c:\project\other\file2.c

output

  c:\project
  ├── file1.c
  ├── other
  │   ├── file2.c
  ├── out
      ├── file1.c
      ├── other
          ├── file2.c

Pre-defined macros

 #define __CAKE__ 202311L
 #define __STDC_VERSION__ 202311L
 #define __STDC_OWNERSHIP__ 1

The define STDC_OWNERSHIP indicates that the compiler suports owneship checks

Pre-defined macros for MSVC compatibility

https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170#standard-predefined-macros

Pre-defined macros for GCC compatibility

https://gcc.gnu.org/onlinedocs/cpp/Predefined-Macros.html

Pre K & R

struct, int, char, float.. https://www.nokia.com/bell-labs/about/dennis-m-ritchie/cman74.pdf https://www.nokia.com/bell-labs/about/dennis-m-ritchie/cman.pdf

K & R

unions

C89

C89 https://port70.net/~nsz/c/c89/c89-draft.html

const, enuns

C95

C95 wide strings (L"...")

C99

https://open-std.org/JTC1/SC22/WG14/www/docs/n1124.pdf

 #define __STDC_VERSION__ 199901L  //C99

C99 restrict pointers

void f(const char* restrict s);

C99 Variable-length array (VLA)

#include <stdlib.h>
#include <stdio.h>

int main() {
    int n = 2;
    int m = 3;
    int (*p)[n][m] = malloc(sizeof * p);

    printf("%zu\n", sizeof(*p));

    free(p);
}
cdd

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n683.htm

Not implemented yet.

C99 Flexible array members


#include <stdio.h>
#include <stdlib.h>

struct X {
    int count;
    double values[]; // flexible array
};

/*
    The size of a structure with a flexible array member is
    determined as if the flexible array member were omitted,
    EXCEPT that it may have more trailing padding than the
    omission would imply
*/

int main() {

    int n = 3;

    printf("sizeof(struct X) = %d\\n", (int) sizeof(struct X));
    printf("allocated = %d\\n", (int) sizeof(struct X) + n * sizeof(double));

    struct X* p = malloc(sizeof(struct X) + n * sizeof(double));
    if (p == NULL) return 0;

    p->count = n;
    p->values[0] = 10.0;
    p->values[1] = 20.0;
    p->values[2] = 30.0;

    for (int i = 0; i < p->count; ++i)
        printf("%f\\n", p->values[i]);

    free(p);

    return 0;
}

C99 static and type qualifiers in parameter array declarators

#include <stdlib.h>

void F(int a[static 5]) {
}

int main() 
{    
    F(0);
    F(NULL);
    F(nullptr);

    int a[] = {1, 2, 3};    
    F(a);//error
    
    int b[] = { 1, 2, 3 , 4, 5};
    F(b); 

    int c[] = { 1, 2, 3 , 4, 5, 6};
    F(c);
}

C99 Complex and imaginary support

Not implemented

C99 Universal character names (\u and \U)

Not implemented

C99 Hexadecimal floating constants

double d = 0x1p+1;

Cake converts hexadecimal floating-point values to decimal floating-point representation using strtod followed by snprintf. This conversion may introduce precision loss.

C99 Compound literals

struct s {
  int i;
};

int f(void) {
  struct s * p = 0, * q;
  int j = 0;
  again:
    q = p, p = & ((struct s) { j++ });
  if (j < 2) goto again;
  return p == q && q -> i == 1;
}

N716 https://www.open-std.org/jtc1/sc22/wg14/www/docs/n716.htm

C99 Designated initializers

 int main()
 {
  int a[6] = {[4] = 29, [2] = 15 };

  struct point { int x, y; };

  struct point p = { .y = 2, .x = 3 }
 }

N494 https://www.open-std.org/jtc1/sc22/wg14/www/docs/n494.pdf

C99 Line comments

Declarations in for loop initializers

int main()
{
   const int max = 10;
   for (int n = max - 1; n >= 0; n--)
   {
     // body of loop
   }
}

C99 inline functions

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n709.htm (30 May 1997) https://www.open-std.org/jtc1/sc22/wg14/www/docs/n741.htm

inline int sum(int a, int b)
{
    return a + b;
}
int main(void)
{
    int r = sum(1, 2);
}

C99 _Pragma preprocessing operator

Not implemented. TODO!

C99 __func__ predefined identifier

N611 13 Sep 96 Mooney, FUNC

#include <stdio.h>
int main()
{
    printf("%s\n", __func__);
    printf("%s\n", __func__);
}

C99 Variadic macros


#include <stdio.h>

#define debug(...) fprintf(stderr, __VA_ARGS__)

int main()
{
  int x = 1;
  debug("X = %d\n", 1);
}

N707 https://www.open-std.org/jtc1/sc22/wg14/www/docs/n707.htm

C99 _Bool

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n815.htm (1998)

int main(void)
{
    _Bool b = 1;
    return 0;
}

C11 Transformations

#define __STDC_VERSION__ 201112L //C11

https://open-std.org/JTC1/SC22/WG14/www/docs/n1570.pdf

https://files.lhmouse.com/standards/ISO%20C%20N2176.pdf

C11 _Static_assert

int main()
{
    _Static_assert(1 == 1, "error");    
}

C11 Anonymous structures and unions

struct v {
  union { /* anonymous union*/
     struct { int i, j; }; /* anonymous structure*/
     struct { long k, l; } w;
  };
  int m;
} v1;

int main(){
  v1.i = 2; /* valid*/
  v1.w.k = 5; /* valid*/
}

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1406.pdf

C11 _Noreturn

_Noreturn void f () {
  abort(); // ok
}

C11 Thread_local/Atomic

Thread_local uses __declspec(thread) in MSVC output and __thread with GCC output.

Atomic - not implemented

C11 type-generic expressions (_Generic)

N1441 https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1441.htm

#include <math.h>

#define cbrt(X) _Generic((X),    \
                  double: cbrtl, \
                  float: cbrtf , \
                  default: cbrtl \
              )(X)


int main(void)
{
    cbrt(1.0);
}

C11 u' ' U' ' character constants

 int i = U'ç';
 int i2 = u'ç';

Important: Cake assume source is utf8 encoded.

C11 u8"literals"

char * s1 = u8"maçã";
char * s2 = u8"maca";

N1488 https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1488.htm

Important: Cake assume source is utf8 encoded.

C11 _Alignof or C23 alignof

 int main()
 {
   int align = alignof(int);
 }

C11 _Alignas or C23 alignas

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1335.pdf

Uses __declspec(align(n)) in MSVC output and attribute((aligned(n))) in GCC output.

C23 Transformations

https://open-std.org/JTC1/SC22/WG14/www/docs/n3096.pdf

#define __STDC_VERSION__ 201710L  //C17
#define __STDC_VERSION__ 202311L  //C23

C23 _Decimal32, _Decimal64, and _Decimal128

Not implemented. https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1107.htm

C23 static_assert / single-argument static_assert

N1330 https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1330.pdf

C23 u8 character prefix

https://open-std.org/JTC1/SC22/WG14/www/docs/n2418.pdf

int main(){
    unsigned char c = u8'~';
}

C23 No function declarators without prototypes

https://www.open-std.org/JTC1/SC22/WG14/www/docs/n2841.htm

int main(){
    func(); //this is an error in C23
}

See also Remove support for function definitions with identifier lists

https://open-std.org/JTC1/SC22/WG14/www/docs/n2432.pdf

C23 Improved Tag Compatibility

Not implemented yet.

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3037.pdf

struct foo { int a; } p;
void bar(void)
{
  struct foo { int a; } q;
  q = p;
}

C23 Unnamed parameters in function definitions

int f(int );

int f(int ) {
}

https://open-std.org/JTC1/SC22/WG14/www/docs/n2480.pdf

C89 backened. We should add a dummy name when generating - Not implemented yet.

C23 Digit separators

int main()
{
    int a = 1000'00;
}

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2626.pdf

C23 Binary literals

#define X  0b1010

int main()
{
    int a = X;
    int b = 0B1010;
}

C23 Introduce the nullptr constant


int main()
{
  void * p = nullptr;
  auto p2 = nullptr;
  typeof(nullptr) p3 = nullptr;
}

https://open-std.org/JTC1/SC22/WG14/www/docs/n3042.htm

C23 Make false and true first-class language features

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2935.pdf

C23 {} empty initializer


int main()
{
    struct X {
        int i;
    } x = {};

    x = (struct X) {};

    struct Y
    {
        struct X x;
    } y = { {} };
}

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2900.htm https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3011.htm

C23 auto

static auto a = 3.5;
auto p = &a;

double A[3] = { 0 };
auto pA = A;
auto qA = &A;

https://open-std.org/JTC1/SC22/WG14/www/docs/n3007.htm

C23 typeof / typeof_unqual


#define SWAP(a, b) \
  do {\
    typeof(a) temp = a; a = b; b = temp; \
  } while (0)


int main()
{
    /*simple case*/
    int a = 1;
    typeof(a) b = 1;

    /*pay attention to the pointer*/
    typeof(int*) p1, p2;

    /*let's expand this macro and see inside*/
    SWAP(a, b);

    /*for anonymous structs we insert a tag*/
    struct { int i; } x;
    typeof(x) x2;
    typeof(x) x3;

   /*Things get a little more complicated*/
   int *array[2];
   typeof(array) a1, a2;
   
   typeof(array) a3[3];
   typeof(array) *a4[4];

   /*abstract declarator*/
   int k = sizeof(typeof(array));

   /*new way to declare pointer to functions?*/
   typeof(void (int)) * pf = NULL;
}

https://open-std.org/JTC1/SC22/WG14/www/docs/n2927.htm https://open-std.org/JTC1/SC22/WG14/www/docs/n2930.pdf

C23 Improved Normal Enumerations

//TODO

https://open-std.org/JTC1/SC22/WG14/www/docs/n3029.htm

enum a {
    a0 = 0xFFFFFFFFFFFFFFFFULL
};

static_assert(_Generic(a0,
        unsigned long long: 0,
        int: 1,
        default: 2 == 0));

The type of the enum must be adjusted.

C23 constexpr

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3018.htm


#include <stdio.h>

constexpr int c = 123;

constexpr int c2 = c + 1000;

int a[c];

constexpr double PI = 3.14;


static_assert(PI + 1 == 3.14 + 1.0);

struct Y {
    int a;
    int ar[3];
    int b;
};

void T3()
{
    constexpr struct Y y = { .ar[1] = 2, 3, 4 };
    static_assert(y.a == 0);
    static_assert(y.ar[0] == 0);
    static_assert(y.ar[1] == 2);
    static_assert(y.ar[2] == 3);
    static_assert(y.b == 4);
    static_assert(y.ar[1] + y.ar[2] == 5);
}

static_assert("abc"[0] == 'a');


int main()
{
    constexpr char ch = 'a';

    printf("%f %c", PI, ch);
}

C23 Enhancements to Enumerations

enum X : short {
  A
};

int main() {
   enum X x = A;   
}

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3030.htm

C23 Attributes

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2335.pdf https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2554.pdf

C23 fallthrough attribute

Not implemented

https://open-std.org/JTC1/SC22/WG14/www/docs/n2408.pdf

C23 deprecated attribute

Partially implemented https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2334.pdf

C23 maybe_unused attribute

Implemented https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2270.pdf

C23 nodiscard attribute

Partially implemented

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2267.pdf

https://open-std.org/JTC1/SC22/WG14/www/docs/n2448.pdf

C23 [[unsequenced]] and [[reproducible]]

//TODO

https://open-std.org/JTC1/SC22/WG14/www/docs/n2956.htm

C23 __has_attribute

C23 __has_include


#if __has_include(<stdio.h>)
#warning  YES
#endif

#if __has_include(<any.h>)
#warning  YES
#else
#warning  NO
#endif

C23 #warning

int main()
{
  #warning my warning message  
}

Implemented
C89 backend - n/a

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2686.pdf

C23 #embed

Partially implemented.

#include <stdio.h>

int main()
{
  static const char file_txt[] = {
   #embed "stdio.h"
   ,0
  };

  printf("%s\n", file_txt);
}

C23 #elifdef #elifndef

Implemented

#define Y

#ifdef X
#define VERSION 1
#elifdef  Y
#define VERSION 2
#else
#define VERSION 3
#endif

C23 __VA_OPT__

Implemented.


#define F(...) f(0 __VA_OPT__(,) __VA_ARGS__)
#define G(X, ...) f(0, X __VA_OPT__(,) __VA_ARGS__)
#define SDEF(sname, ...) S sname __VA_OPT__(= { __VA_ARGS__ })
#define EMP


void f(int i, ...) {}


int main()
{
  int a = 1;
  int b = 2;
  int c = 3;
  
  F(a, b, c);
  F();
  F(EMP);
  G(a, b, c);
  G(a, );
  G(a);

}

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3033.htm

C23 BitInt(N))

Not implemented

C23 Compound Literals with storage specifier

Not implemented yet.

void F(int *p){}

int main()
{
   F((static int []){1, 2, 3, 0})
}

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3038.htm

C23 Variably-modified (VM) types

Not implemented https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2778.pdf

C2Y Transformations

Obsolete implicitly octal literals


static_assert(0o52 == 052);
static_assert(0O52 == 052);
static_assert(0O52 == 42);

int main()
{
    int i = 0o52;
}

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3353.htm

case range expressions

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3370.htm

#def

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3524.txt

_Countof operator

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3369.pdf

Obs: Cake extends countof to enums, returning the number of enumerators.

defer

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3199.htm

defer will call the defer statement before the block exit at inverse order of declaration.

     defer-statement:
        defer secondary-block

For instance:

#include <stdio.h>

int main() {
  do {
     FILE* f = fopen("in.txt", "r");
     if (f == NULL) break;
     defer fclose(f);

     FILE* f2 = fopen("out.txt", "w");
     if (f2 == NULL) break;
     defer fclose(f2);
     //...    
  }
  while(0);
}

Function literals and local functions

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3645.pdf

if declarations, v4

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3388.htm

#include <stdio.h>
int main()
{
   int size = 10;
   if (FILE* f = fopen("file.txt", "r"); f)
   {
     /*...*/
     fclose(f);
   }
}

C++ proposal https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0305r0.html

C2Y typename on _Generic

This feature was created in Cake and now it is part of C2Y!

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3260.pdf

 int main()
{
    const int * const p;
    static_assert(_Generic(p, const int *: 1));

    /*extension*/
    static_assert(_Generic(int, int : 1));
    static_assert(_Generic(typeof(p), const int * const: 1));
}

Cake Extensions (Not in C23, C2Y)

Extension - try catch throw

   try-statement:
      try secondary-block
      try secondary-block catch secondary-block   

jump-statement:
  throw;

try catch is a external block that we can jump off.

try catch is a LOCAL jump this is on purpose not a limitation.

catch block is optional.

try
{
   for (int i = 0 ; i < 10; i++) {
      for (int j = 0 ; j < 10; j++) {
        ... 
        if (error) throw;
        ...
      }
   }
}
catch
{
}

Extension #pragma dir

#pragma dir "C:/Program Files (x86)/Windows Kits/10//include/10.0.22000.0/cppwinrt"

pragma dir makes the preprocessor include the directory when searching for includes.

Type traits

We have some compile time functions to infer properties of types.


_is_char()
The three types char, signed char, and unsigned char are collectively called the character types.

_is_pointer
Pointer to object or function

_is_array
Array type

_is_function
A function type describes a function with specified return type. 

_is_floating_point
float, double, and long double return true

_is_integral
The standard signed integer types and standard unsigned integer types are collectively called the
standard integer types;

_is_arithmetic
Integer and floating types are collectively called arithmetic types. 

_is_scalar
Arithmetic types, pointer types, and the nullptr_t type are collectively called scalar types

Note: Type traits that can be easily created with _Generic will be removed. _

Extension - Object lifetime checks

See ownership

_Owner
_Opt
_View

GCC extensions

These GCC extensions allow parsing headers and generate correct code for GCC 

__builtin_va_list
__builtin_c23_va_start
__builtin_va_start
__builtin_va_end
__builtin_va_arg
__builtin_va_copy

__builtin_offsetof
__attribute__
__typeof__ alias for typeof in cake

MSVC extensions

__ptr32, __ptr64
__int8 ... __int64
__declspec
__cdecl
__fastcall, __stdcall
__forceinline alias for inline in cake

Extension assert built-in

In cake assert is an built-in function. The reason is because it works as tips for flow analysis.

For instance, in a linked list when head is null tail is also null, and tail->next always points to null.

Assertion will check these properties in runtime and also make the static analysis assume that assert evaluates to true.


void list_push_back(struct list* list,
                    struct item* _Owner p_item)
{
   if (list->head == NULL) {
      list->head = p_item;
   }
   else {
      assert(list->tail != nullptr);
      assert(list->tail->next == nullptr);
      list->tail->next = p_item;
   }
   list->tail = p_item;
}

However, assert is not a "blind override command." In situations like:

    int i = 0;
    assert(i != 0);

In situations where static analysis can identify two or more possible states, assert works as a state selector, similar to what happens in if statements but without the scope.

    void f(int * _Opt p)
    {
        if (p != NULL) {
           //p is not null here...
        }
    }
    
    void f2(int * _Opt p)
    {
        assert(p != NULL);
        //we assume p is not null here...        
    }