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Compilation error

Posted on 2003-12-04
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Last Modified: 2010-04-15
1. The below code is OK if compiled in ANSI C Compiler but not on normal C Compiler. What's the solution for this problem?

char buf[100];

if ((numbytes=recv(new_fd, buf, 100-1, 0)) == -1) {
   perror("recv");
  exit(1);
}

buf[numbytes] = '\0';
printf("Received: %s\n",buf);

char *search_str = buf; ==> error at this line
--------------------------------------------------
error 1000: Unexpected symbol: "char".
error 1588: "search_str" undefined.
--------------------------------------------------

printf("search_str == %s\n", search_str); ==> error at this line
---------------------------------------------------
error 1549: Modifiable lvalue required for assignment operator.
---------------------------------------------------

2. Can anybody explain to me or suggest to me for any good interactive tutorial on pointer?
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Question by:showbix
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11 Comments
 
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Expert Comment

by:sunnycoder
ID: 9873531
Hi showbix,

I presume you meant not compiling in ANSI C but compiling in "normal" C

1. in C all declarations must precede the first statement...
To be more specific declarations are allowed only at the beginning of a "block"

2. you cannot assign strings like a=b ... nor can you compare them like a==b ... you have to use strcpy and strcmp respectively

http://www.cs.cf.ac.uk/Dave/C/CE.html
is a good tutorial

Cheers!
Sunny:o)
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LVL 45

Expert Comment

by:sunnycoder
ID: 9873562
just noticed that you were not assigning strings there ... just  pointer manipulation ... that will work fine once search_str is declared properly ...

move char * search_str to the beginning of the function and everything should work well.
0
 
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Expert Comment

by:Mayank S
ID: 9874047
>> 1. in C all declarations must precede the first statement...

But Sunny, that was old.... the latest accepted standard C99 overrides it. It is now legal in C to declare variables anywhere in a program, in any block. However, all compilers don't support it as yet.
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LVL 45

Expert Comment

by:sunnycoder
ID: 9874075
> It is now legal in C to declare variables anywhere in a program, in any block.
Nope mayank ... Variables can be declared only at the *beginning* of a block
C++ permits you to declare variables anywhere in the program but C still requires declarations to be at the beginning of a block
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Expert Comment

by:Mayank S
ID: 9879830
Ok, sorry I got confused with program and block :-), so I thought that you were wrong.

Anyways, Sunny, pls comment on: http://www.experts-exchange.com/Programming/Q_20816080.html
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LVL 45

Expert Comment

by:sunnycoder
ID: 9880190
sorry mayank ... I do not have much idea about java or .net
I am still limited to C and linux
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Expert Comment

by:Mayank S
ID: 9880300
ok, no worries :-)
0
 

Author Comment

by:showbix
ID: 9880797
Hey guys,
Let me explain what I need to achieve here.

I read the data using recv function and insert it into buf variable
---------------------------------------------------------------------
char buf[100];


if ((numbytes=recv(new_fd, buf, 100-1, 0)) == -1) {
   perror("recv");
   exit(1);
}

buf[numbytes] = '\0';
printf("Received: %s\n",buf);

char *search_str = buf;

if (strstr(search_str,"SUCCESS") != NULL)
{
  printf("SUCCESS found\n");
}
  else
{
  printf("SUCCESS not found\n");
}

---------------------------------------------------------------------
I tried to copy the buf value into search_str so that I can perform the sub-string search.
From search_str variable I would like to scan a sub-string (e.g SUCCESS).

The code above works fine in ANSI C compiler but it throw me erros when using normal C Compiler.
The error is at this line --- char *search_str = buf;

Putting the declaration "char *search_str = buf;" at the beginning of function will need me to put another statement(which I dont know) to copy the buf value into the search_str variable.
 

How do I rectify it so that the program works?

FYI, I'm in the UNIX environment.




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LVL 30

Assisted Solution

by:Mayank S
Mayank S earned 25 total points
ID: 9880914
char buf[100] ;
char * search_str = NULL ;

if ((numbytes=recv(new_fd, buf, 100-1, 0)) == -1) {
   perror("recv");
   exit(1);
}

buf[numbytes] = '\0';
printf("Received: %s\n",buf);

search_str = buff ;
0
 
LVL 45

Accepted Solution

by:
sunnycoder earned 25 total points
ID: 9880916
>Putting the declaration "char *search_str = buf;" at the beginning of function will need me to put another statement(which I
>dont know) to copy the buf value into the search_str variable.
just move the declaration to the beginning and let the assignment remain as it is


char buf[100];
char * search_str; //declaration here

if ((numbytes=recv(new_fd, buf, 100-1, 0)) == -1) {
  perror("recv");
  exit(1);
}

buf[numbytes] = '\0';
printf("Received: %s\n",buf);

search_str = buf;     //assignment remains

if (strstr(search_str,"SUCCESS") != NULL)
{
 printf("SUCCESS found\n");
}
 else
{
 printf("SUCCESS not found\n");
}
0
 
LVL 30

Expert Comment

by:Mayank S
ID: 9880917
On second thought:

char buf[100] ;
char * search_str = buf ;

if ((numbytes=recv(new_fd, buf, 100-1, 0)) == -1) {
   perror("recv");
   exit(1);
}

buf[numbytes] = '\0';
printf("Received: %s\n",buf);

// because 'buf' will always have the same base address,so it can be assigned to search_str right at the start, after declaration.
0

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