Programming Forums > Application Development > C

lgiordano · Jul 13th, 2005, 7:59 AM

Hi, this is my problem:
I have two programms (both made by me): my main application and an external one. The external one must read the main app version. The version is declared as: #define APP_VERSION (XX). I dont know very much about compilers/linkers, but I think that the defines are not mapped into the exe. However, I use APP_VERSION to print in some places of my app, so somewhere in exe it should appear. But, as the main app changes some code in new versions, I can't read in a some fixed exe position, and be sure to always read version ok.
My question is, how can I make some code, or tell the compiler/linker to map a constant in the exe in an fixed position? Until now, I am doing this:

(Toggle Plain Text)

main() 
{
  /* I only use this printf() to print version, not because I want to show it */
  /* here, but to make it appear in the exe in a fixed pos, as it is the first */  
  /* instruction executed, so it is easy to find it in exe */
  printf("%d", APP_VERSION); 
...
...

}

Best wishes from Argentina!

DaWei · Jul 13th, 2005, 8:44 AM

Why don't you just declare a local variable there and initialize it to the version number? Essentially, that's what you're doing with the parameter to "printf".

Infinite Recursion · Jul 13th, 2005, 8:49 AM

If the main app is always running, you can use an environment variable...

(Toggle Plain Text)

The following example changes the value of the HOME environment variable to the value /usr/home.

#include <stdlib.h>
...
static char *var = "HOME=/usr/home";
int ret;

ret = putenv(var);

jim mcnamara · Jul 13th, 2005, 9:51 AM

I think he means something like fingerprinting or image file version identifiers.

Let's try the easiest one put a what string at the beginning of a string. Put this near the top of your code

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static char *MYidentifier="@(#) programname version 1.1.0";

ident and what will display it for you. You can write your own ident module -
call strstr() to find the start of the identifier.

lgiordano · Jul 13th, 2005, 9:58 AM

Thanks for the replies.
DaWei, before doing the printf() I had tought about your suggestion. However, I wasn't sure about compiler's optimization, so if I declare a variable but I dont use, the compiler may eliminate it, even when I initialized it. Certainly I could do this:

(Toggle Plain Text)

main()
{
  unsigned int nVer = APP_VERSION;
  nVer = nVer; // Compiler, optimize all but no this!
}

I can also add some ASM code, I will test it.
By the way, please correct me if I am wrong, I think there is a way to tell the linker to add a fixed block in a fixed position in the exe.

Regards,

Jul 13th, 2005, 7:59 AM	#1
lgiordano Newbie Join Date: Feb 2005 Posts: 8 Rep Power: 0	Read Programm Version from outside Hi, this is my problem: I have two programms (both made by me): my main application and an external one. The external one must read the main app version. The version is declared as: #define APP_VERSION (XX). I dont know very much about compilers/linkers, but I think that the defines are not mapped into the exe. However, I use APP_VERSION to print in some places of my app, so somewhere in exe it should appear. But, as the main app changes some code in new versions, I can't read in a some fixed exe position, and be sure to always read version ok. My question is, how can I make some code, or tell the compiler/linker to map a constant in the exe in an fixed position? Until now, I am doing this: (Toggle Plain Text) main() { /* I only use this printf() to print version, not because I want to show it / / here, but to make it appear in the exe in a fixed pos, as it is the first / / instruction executed, so it is easy to find it in exe / printf("%d", APP_VERSION); ... ... } main() { / I only use this printf() to print version, not because I want to show it / / here, but to make it appear in the exe in a fixed pos, as it is the first / / instruction executed, so it is easy to find it in exe */ printf("%d", APP_VERSION); ... ... } Best wishes from Argentina!

Jul 13th, 2005, 8:44 AM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Why don't you just declare a local variable there and initialize it to the version number? Essentially, that's what you're doing with the parameter to "printf". __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jul 13th, 2005, 8:49 AM	#3
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	If the main app is always running, you can use an environment variable... (Toggle Plain Text) The following example changes the value of the HOME environment variable to the value /usr/home. #include <stdlib.h> ... static char var = "HOME=/usr/home"; int ret; ret = putenv(var); The following example changes the value of the HOME environment variable to the value /usr/home. #include <stdlib.h> ... static char var = "HOME=/usr/home"; int ret; ret = putenv(var); __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Jul 13th, 2005, 9:51 AM	#4
jim mcnamara Hobbyist Programmer Join Date: Jun 2005 Location: New Mexico Posts: 228 Rep Power: 4	I think he means something like fingerprinting or image file version identifiers. Let's try the easiest one put a what string at the beginning of a string. Put this near the top of your code (Toggle Plain Text) static char MYidentifier="@(#) programname version 1.1.0"; static char MYidentifier="@(#) programname version 1.1.0"; ident and what will display it for you. You can write your own ident module - call strstr() to find the start of the identifier.

Jul 13th, 2005, 9:58 AM	#5
lgiordano Newbie Join Date: Feb 2005 Posts: 8 Rep Power: 0	Thanks for the replies. DaWei, before doing the printf() I had tought about your suggestion. However, I wasn't sure about compiler's optimization, so if I declare a variable but I dont use, the compiler may eliminate it, even when I initialized it. Certainly I could do this: (Toggle Plain Text) main() { unsigned int nVer = APP_VERSION; nVer = nVer; // Compiler, optimize all but no this! } main() { unsigned int nVer = APP_VERSION; nVer = nVer; // Compiler, optimize all but no this! } I can also add some ASM code, I will test it. By the way, please correct me if I am wrong, I think there is a way to tell the linker to add a fixed block in a fixed position in the exe. Regards,

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Programming Forums > Application Development > C

Read Programm Version from outside