Question

For some reason this line of code is giving me quite a problem.

struct socketaddr_in clientaddr;

The error message is:

tiny.c:23:24: error: storage size of ‘clientaddr’ isn’t known

If I remove that line of code I get the following error message:

s2s2@s2s2-ThinkPad-T61:~/Documents/Cprogramming/web_server$ make
gcc -std=gnu99 -O2 -lpthread -lrt -o server tiny.c csapp.c
/tmp/ccVxw07i.o: In function `Pthread_create':
csapp.c:(.text+0x7e5): undefined reference to `pthread_create'
/tmp/ccVxw07i.o: In function `Pthread_cancel':
csapp.c:(.text+0x805): undefined reference to `pthread_cancel'
/tmp/ccVxw07i.o: In function `Pthread_join':
csapp.c:(.text+0x825): undefined reference to `pthread_join'
/tmp/ccVxw07i.o: In function `Pthread_detach':
csapp.c:(.text+0x845): undefined reference to `pthread_detach'
/tmp/ccVxw07i.o: In function `Sem_init':
csapp.c:(.text+0x895): undefined reference to `sem_init'
/tmp/ccVxw07i.o: In function `P':
csapp.c:(.text+0x8b5): undefined reference to `sem_wait'
/tmp/ccVxw07i.o: In function `V':
csapp.c:(.text+0x8d5): undefined reference to `sem_post'
/tmp/ccVxw07i.o: In function `Pthread_once':
csapp.c:(.text+0x881): undefined reference to `pthread_once'
collect2: ld returned 1 exit status
make: *** [webServer-gcc] Error 1

Here are links to the csapp.c and csapp.h files.

Thanks for all the help.

Answer 1

tiny.c:23:24: error: storage size of ‘clientaddr’ isn’t known

There’s a reason you need to declare structs as struct structname instancename in C – that’s so that the C compiler knows how much memory to allocate – and possibly how to align that data, etc.

This is the C compiler’s way of telling you no such struct socketaddr_in exists – it’d be sockaddr_in.

A common way to work around the naming of structs in this way is to define them like this:

typedef struct _struct_name
{
    /* ... */
} structname;

then structname can be used as a type without the struct qualifier. You don’t have to do this on the definition of the struct, either, you could do it later.

So, the short answer is socketaddr_in doesn’t exist as a struct in POSIX – it’s sockaddr_in.