Problems using getaddrinfo and friends using c99 standard

[Nathan]

Hi,

I'm trying to do some network programming, but when I use 'struct
addrinfo' or getaddrinfo, I see errors:
[ ~/src/_sandbox] gcc --std=c99 -Wall ipv6_test.c -o it
ipv6_test.c: In function `main':
ipv6_test.c:25: error: storage size of 'hints' isn't known
ipv6_test.c:34: warning: implicit declaration of function
`getaddrinfo'
ipv6_test.c:38: error: dereferencing pointer to incomplete type
ipv6_test.c:39: error: dereferencing pointer to incomplete type
ipv6_test.c:40: error: dereferencing pointer to incomplete type
ipv6_test.c:41: error: dereferencing pointer to incomplete type
ipv6_test.c:49: error: dereferencing pointer to incomplete type
ipv6_test.c:49: error: dereferencing pointer to incomplete type
ipv6_test.c:49: error: dereferencing pointer to incomplete type
ipv6_test.c:56: warning: implicit declaration of function
`gai_strerror'
ipv6_test.c:56: warning: format argument is not a pointer (arg 4)
ipv6_test.c:71: error: dereferencing pointer to incomplete type
ipv6_test.c:71: error: dereferencing pointer to incomplete type
ipv6_test.c:77: warning: implicit declaration of function
`freeaddrinfo'
ipv6_test.c:25: warning: unused variable `hints'

However, it builds fine when I remove --std-c99

Does anyone know the reason for this?

Thanks,
Nathan

 

[Antoninus Twink]

I'm trying to do some network programming, but when I use 'struct
addrinfo' or getaddrinfo, I see errors: [snip]
ipv6_test.c:34: warning: implicit declaration of function `getaddrinfo' [snip]
ipv6_test.c:56: warning: implicit declaration of function `gai_strerror' [snip]
ipv6_test.c:77: warning: implicit declaration of function `freeaddrinfo'

You're probably not including the reqired headers. Try

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>

 

[Harald van Dijk]

I'm trying to do some network programming, but when I use 'struct
addrinfo' or getaddrinfo, I see errors: [snip]
ipv6_test.c:34: warning: implicit declaration of function `getaddrinfo' [snip]
ipv6_test.c:56: warning: implicit declaration of function
`gai_strerror' [snip]
ipv6_test.c:77: warning: implicit declaration of function
`freeaddrinfo'

You're probably not including the reqired headers. Try

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>

The OP probably is including the required headers, or the compiler would
also have complained without the --std-c99 option. The answer is simply
that getaddrinfo is not a C99 function, and is therefore not declared by
the library when asking for a C99 implementation.

 

[Antoninus Twink]

The OP probably is including the required headers, or the compiler would
also have complained without the --std-c99 option. The answer is simply
that getaddrinfo is not a C99 function, and is therefore not declared by
the library when asking for a C99 implementation.

I think you're right. That seems like a terrible misfeature of gcc. If I
have a C program and I include a POSIX header, I damn well want the
functions from that header, in just the same way as if I include my own
header file then I want access to those functions, without the compiler
getting all holier-than-thou and telling me my functions aren't
mentioned in the C standard.

One solution is to add -D_POSIX_C_SOURCE=200112L as a command-line
option.

 

[Nathan]

One solution is to add -D_POSIX_C_SOURCE=200112L as a command-line
option.

Harald is correct. I had included the required headers.

Antoninus, your solution does work, but unless I have to I would
prefer to avoid defining a (to me) obscure symbol in order to make a
standard POSIX function work. Like you said, I don't appreciate the
"feature" of gcc denying me access to these functions just because my
company uses the c99 standard.

Thanks for the help, and I'll use the above solution as a stopgap
unless (hopefully until) someone comes up with something better.

Nathan