...access section addresses from C or C++?

Follow

Paul Curtis

• July 13, 2009 12:14

How can I determine the start and end addresses of a section from within a program?

 

The CrossWorks for ARM linker script generator creates __section_name_start__ and __section_name_end__ symbols to mark the start and end of each section.

As an example, if you want to set a pointer to the start address of the .text section you could use the following code:

extern unsigned char __text_start__;

void
func(void)
{
  unsigned char *ptr = &__text_start__;
  ...
}

0

• 

  John Wood

  • September 14, 2009 10:17

  I'm using CrossStudio 1.3 for MSP430, and want to use the start and end of my CODE section in my C code. I've tried using &__CODE_end__ without success. Have I got a wrong character somewhere, or does this not work in my version?

   

  Thanks John

  0

  Comment actions Permalink
• 

  Stephen Hersey

  • July 15, 2011 15:01

  The above reference code works for CrossWorks 2.0, but generates a compiler warning when used under Crossworks 2.1; since I'm required to compile using "-Wall", this generates an error and kills my build. Is there a simple solution other than disabling the -Wall option?

   

  I'd like to try casting the void object to a uint8_t in order to take its address, as in the sample below, but I'm unsure if this is wise, being somewhat unfamiliar with entities of type void. Will this code work reliably and safely?

   

  extern void __text_start__;
  
  void
  func(void)
  {
    unsigned long *ptr = &(uint8_t)(__text_start__);
    ...
  }

  0

  Comment actions Permalink
• 

  Stephen Hersey

  • July 15, 2011 15:27

  Well, the casting trick I mention above won't work; the compiler complains that __text_start__ is not a complete type.

  I've also tried the #pragma GCC diagnostic  ignore "-Werror" route, but while the compiler WILL complain if the pragma is malformed, it WON'T actually prevent the compiler error on the original reference code, regardless of what the GCC docs say about diagnostic pragmas overriding command-line options. The best solution now appears to be to set the "Treat warnings as errors" property for the affected files to "No" in the Properties pane of the IDE.

  0

  Comment actions Permalink
• 

  Michael Johnson

  • July 15, 2011 16:44

  Try

  extern unsigned __text_start__[];

  should be okay with C nor sure about C++

  0

  Comment actions Permalink
• 

  Stephen Hersey

  • July 15, 2011 17:19

  Thanks! That seems to work. As I'm working in C, C++ isn't an issue.

  If I understand the situation correctly, we could declare __text_start__ to be of any type we please here. Since all that we do is take its address, the fact that there's no actual variable (just an address with that name) won't matter, and the compiler and linker will be happy.

  0

  Comment actions Permalink
• 

  Michael Johnson

  • July 16, 2011 08:24

  Correct. I'm moving over to use the unsigned[]  This was Paul's suggestion as it avoids warnings (in context I use it) and doesn't look too odd.

  0

  Comment actions Permalink
• 

  Jgros

  • March 08, 2013 18:12

  For those working with the MSP430 the syntax is

   

  extern unsigned char __begin_SECTIONNAME[];

  extern unsigned char __end_SECTIONNAME[];

   

  if you had a section called SECTIONNAME in your section placement file.

  0

  Comment actions Permalink

Please sign in to leave a comment.