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Text resources and linker optimization

Sven Petersen

Hi there!

At present I am writing a program in C51 that might be available in different language versions one day. So I place all texts in one file called texts.h.

That file looks like
[...]

#define    OK_STR     "ok"
#define    CRLF_STR   "\x0D\x0a"

#define    MODEM_STR  "Modem"
[...]

Many of those strings are used several times in different C source files. Now my question... will those strings be located in one address in the code memory or will they be located once per module where they are used or will they be located for every time I use them?

I guess, I could make sure that a string only occures once in the code by creating constants in code space in a texts.c and make them public as global constants in texts.h. But that would be the harder way, since I have to type that string constant name at least three times (texts.c, texts.h and where I use them).

So, how does the linker optimize the string constants?

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  • 0

    I presume what you're looking for is an equivalent of Borland's "Merge Duplicate Strings" option?

    AFAIK, Keil does not have an equivalent option; ie, every time you write a string literal it will occupy a separate area of code memory.

    Therefore, you will have to adopt your texts.c + texts.h approach:

    But that would be the harder way, since I have to type that string constant name at least three times (texts.c, texts.h and where I use them).

    But using your original #define approach would still require typing the names where you define them and where you use them; it's not really that much extra effort, is it?
    And the texts.h file could very easily be created by simply editing your texts.c file, and removing the initialisations.
    In fact, if you're that worried, you could write a macro which allow you to just type once and serve both purposes!

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  • 0

    I presume what you're looking for is an equivalent of Borland's "Merge Duplicate Strings" option?

    AFAIK, Keil does not have an equivalent option; ie, every time you write a string literal it will occupy a separate area of code memory.

    Therefore, you will have to adopt your texts.c + texts.h approach:

    But that would be the harder way, since I have to type that string constant name at least three times (texts.c, texts.h and where I use them).

    But using your original #define approach would still require typing the names where you define them and where you use them; it's not really that much extra effort, is it?
    And the texts.h file could very easily be created by simply editing your texts.c file, and removing the initialisations.
    In fact, if you're that worried, you could write a macro which allow you to just type once and serve both purposes!

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