CCS C Software and Maintenance Offers
FAQFAQ   FAQForum Help   FAQOfficial CCS Support   SearchSearch  RegisterRegister 

ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

CCS does not monitor this forum on a regular basis.

Please do not post bug reports on this forum. Send them to support@ccsinfo.com

strlen() on ROM strings

 
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion
View previous topic :: View next topic  
Author Message
bdeb



Joined: 05 Nov 2010
Posts: 36
Location: Sweden

View user's profile Send private message Visit poster's website

strlen() on ROM strings
PostPosted: Sat Mar 19, 2022 2:14 pm     Reply with quote

CCS 5.107
MPLAB-X 5.50
18F16Q41

Sorry for stupid question, not a problem that an extra strcpy() can't fix, but I'd like to know why...

NOTES:
PASS_STRINGS=IN_RAM is defined
I have "u8" defined as unsigned int8, "s8" as signed int8, etc

Code:

const char LookUp[3][20] = {"Text5", "String7", "LongData9" };

u8 idx = 0;
u8 cmdlen = 0;


   for (idx=0; idx<3; idx++)
   {
      cmdlen=strlen(LookUp[idx] );
      fprintf(PC,"[%d] Len=%d Txt=%s\r\n", idx, cmdlen, LookUp[idx]);
   }



This prints:

[0] Len=5 Txt=Text5
[1] Len=6 Txt=String7
[2] Len=6 Txt=LongData9

What gives?
Is strlen() not "overloaded" like printf() to handle ROM->RAM?
And why does it work <=6 ??

I need even more coffee..

All the best:

/Björn
hmmpic



Joined: 09 Mar 2010
Posts: 314
Location: Denmark

View user's profile Send private message

PostPosted: Sun Mar 20, 2022 4:49 am     Reply with quote

In the past i have the same problem with const, maybe some of the more clever one can explain about it.

You can remove the const and it work, or you can use rom as this:

Code:

rom char LookUp[3][20] = {"Text5", "String7", "LongData9" };
char buff[21];

int8 idx = 0;
int8 cmdlen = 0;

   for (idx=0; idx<3; idx++)
   {
      read_program_memory(LookUp[idx],&Buff,20);
      cmdlen=strlen(buff);
      printf("StrLenTest: [%u] Len=%u Txt=%s\r\n", idx, cmdlen, buff);
   }
}



or:

Code:

void strlentest(){

const char LookUp[3][20] = {"Text5", "String7", "LongData9" };
char buff[21];

int8 idx = 0;
int8 cmdlen = 0;

   for (idx=0; idx<3; idx++)
   {
     sprintf(buff,LookUp[idx]);
     cmdlen=strlen(buff);
     printf("StrLenTest [%u] Len=%u Txt=%s\r\n", idx, cmdlen, buff);
   }
}
bdeb



Joined: 05 Nov 2010
Posts: 36
Location: Sweden

View user's profile Send private message Visit poster's website

PostPosted: Sun Mar 20, 2022 6:19 am     Reply with quote

Thank you hmmpic,

I use a variant of your second example, but with strcpy().

BTW Congrats to Kevin being back in F1! Very Happy
Ttelmah



Joined: 11 Mar 2010
Posts: 19195

View user's profile Send private message

PostPosted: Sun Mar 20, 2022 10:28 am     Reply with quote

I'm actually surprised your code compiled.
I'd have expected there to have been a compiler error that you are
attempting to construct a pointer to rom.
Now 'pass strings' works to virtualise a string, but does it using a very
small buffer. What is happening is this doesn't realise you want a whole
string, so virtualises just the start, expecting to be called again, when the
rest of the string is needed, but strlen doesn't actually access the
virtual string, instead making it's own pointer to this. Unfortunately
this means the extra virtualisation doesn't then happen.
rom as against const, does allow pointers to be constructed. However
they are rom pointers, so normally do need functions specifically written
to use these. hmmpic's code virtualises these to ram.
As you say, strcpy can be used to do the same virtualisation and is
a simple fix.
bdeb



Joined: 05 Nov 2010
Posts: 36
Location: Sweden

View user's profile Send private message Visit poster's website

PostPosted: Sun Mar 20, 2022 11:43 am     Reply with quote

Thank you Ttelmah - just made me a little wiser!

Smile

/Björn
Display posts from previous:   
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group