Syntax

Single Line:

              .cdecls [options ,] " filename "[, " filename2 "[,...]]

Syntax

Multiple Lines:

              .cdecls [options]

       %{

              /*---------------------------------------------------------------------------------*/

              /* C/C++ code - Typically a list of #includes and a few defines */

              /*---------------------------------------------------------------------------------*/

       %}

Description

The .cdecls directive allows programmers in mixed assembly and C/C++ environments to share C headers containing declarations and prototypes between the C and assembly code. Any legal C/C++ can be used in a .cdecls block and the C/C++ declarations cause suitable assembly to be generated automatically, allowing you to reference the C/C++ constructs in assembly code; such as calling functions, allocating space, and accessing structure members; using the equivalent assembly mechanisms. While function and variable definitions are ignored, most common C/C++ elements are converted to assembly, for instance: enumerations, (non-function-like) macros, function and variable prototypes, structures, and unions.

The .cdecls options control whether the code is treated as C or C++ code; and how the .cdecls block and converted code are presented. Options must be separated by commas; they can appear in any order:

In the single-line format, the options are followed by one or more filenames to include. The filenames and options are separated by commas. Each file listed acts as if #include "filename" was specified in the multiple-line format.

In the multiple-line format, the line following .cdecls must contain the opening .cdecls block indicator %{. Everything after the %{, up to the closing block indicator %}, is treated as C/C++ source and processed. Ordinary assembler processing then resumes on the line following the closing %}.

The text within %{ and %} is passed to the C/C++ compiler to be converted into assembly language. Much of C language syntax, including function and variable definitions as well as function-like macros, is not supported and is ignored during the conversion. However, all of what traditionally appears in C header files is supported, including function and variable prototypes; structure and union declarations; non-function-like macros; enumerations; and #defines.

The resulting assembly language is included in the assembly file at the point of the .cdecls directive. If the LIST option is used, the converted assembly statements are printed in the listing file.

The assembly resulting from the .cdecls directive is treated similarly to a .include file. Therefore the .cdecls directive can be nested within a file being copied or included. The assembler limits nesting to ten levels; the host operating system may set additional restrictions. The assembler precedes the line numbers of copied files with a letter code to identify the level of copying. An A indicates the first copied file, B indicates a second copied file, etc.

The .cdecls directive can appear anywhere in an assembly source file, and can occur multiple times within a file. However, the C/C++ environment created by one .cdecls is not inherited by a later .cdecls; the C/C++ environment starts new for each .cdecls.

See Chapter 13 for more information on setting up and using the .cdecls directive with C header files.

Example

In this example, the .cdecls directive is used call the C header.h file.

C header file:

#define WANT_ID 10
#define NAME "John\n"
extern int a_variable;
extern float cvt_integer(int src);
struct myCstruct { int member_a; float member_b; };
enum status_enum { OK = 1, FAILED = 256, RUNNING = 0 };

Source file:

         .cdecls C,LIST,"myheader.h"
size:    .int $sizeof(myCstruct)
aoffset: .int myCstruct.member_a 
boffset: .int myCstruct.member_b
okvalue: .int status_enum.OK
failval: .int status_enum.FAILED
         .if $defined(WANT_ID)
id       .cstring NAME
         .endif

Listing File:

       1                      .cdecls C,LIST,"myheader.h"
 A     1              ; ------------------------------------------
 A     2              ; Assembly Generated from C/C++ Source Code
 A     3              ; =========== MACRO DEFINITIONS ===========
 A     4                         .define "1",_OPTIMIZE_FOR_SPACE 
 A     5                         .define "1",__ASM_HEADER__ 
 A     6                         .define "1",__edg_front_end__ 
 A     7                         .define "5001000",__COMPILER_VERSION__ 
 A     8                         .define "0",__TI_STRICT_ANSI_MODE__ 
 A     9                         .define """14:53:42""",__TIME__ 
 A    10                         .define """I""",__TI_COMPILER_VERSION_QUAL__ 
 A    11                         .define "unsigned long",__SIZE_T_TYPE__ 
 A    12                         .define "long",__PTRDIFF_T_TYPE__ 
 A    13                         .define "1",__TMS320C2000__ 
 A    14                         .define "1",_TMS320C28X 
 A    15                         .define "1",_TMS320C2000 
 A    16                         .define "1",__TMS320C28X__ 
 A    17                         .define "1",__STDC__ 
 A    18                         .define "1",__signed_chars__ 
 A    19                         .define "0",__GNUC_MINOR__ 
 A    20                         .define "1",_TMS320C28XX 
 A    21                         .define "5001000",__TI_COMPILER_VERSION__ 
 A    22                         .define "1",__TMS320C28XX__ 
 A    23                         .define "1",__little_endian__ 
 A    24                         .define "199409L",__STDC_VERSION__ 
 A    25                         .define """EDG gcc 3.0 mode""",__VERSION__ 
 A    26                         .define """John\n""",NAME 
 A    27                         .define "unsigned int",__WCHAR_T_TYPE__ 
 A    28                         .define "1",__TI_RUNTIME_RTS__ 
 A    29                         .define "3",__GNUC__ 
 A    30                         .define "10",WANT_ID 
 A    31                         .define """Sep  7 2007""",__DATE__ 
 A    32                         .define "7250",__TI_COMPILER_VERSION_QUAL_ID__ 
 A    33              
 A    34              ; =========== TYPE DEFINITIONS ===========
 A    35              status_enum   .enum                
 A    36        0001  OK            .emember 1           
 A    37        0100  FAILED        .emember 256         
 A    38        0000  RUNNING       .emember 0           
 A    39                            .endenum             
 A    40              
 A    41              myCstruct     .struct 0,2 ; size=4 bytes|64 bits, align=2
 A    42        0000  member_a      .field 16 ; int- offset 0, size 1 byte
 A    43        0001                .field 16 ; padding
 A    44        0002  member_b      .field 32 ; float- offset 2 byte,size 2 byte
 A    45        0004                .endstruct  ; final size=(4 bytes|64 bits)
 A    46              
 A    47              ; =========== EXTERNAL FUNCTIONS ===========
 A    48                               .global _cvt_integer 
 A    49              
 A    50              ; =========== EXTERNAL VARIABLES ===========
 A    51                               .global _a_variable  
       2 00000000 0004  size: .int $sizeof(myCstruct)
       3 00000001 0000  aoffset: .int myCstruct.member_a
       4 00000002 0002  boffset: .int myCstruct.member_b
       5 00000003 0001  okvalue: .int status_enum.OK
       6 00000004 0100  failval: .int status_enum.FAILED
       7                      .if $defined(WANT_ID)
       8 00000005 004A  id .cstring NAME
         00000006 006F 
         00000007 0068 
         00000008 006E 
         00000009 000A 
         0000000a 0000 
       9                      .endif