Differences is using netdb.h with the cc and gcc compilers.

[Ravi Desai]

I have a small 'C' program that wraps up the netdb.h headers on
multiple
platforms. The AIX version of this code compiles beautifully using
the AIX
cc compiler. However, I've recently downloaded gcc and am trying to
port
over to using the gcc compiler on all the platforms I can get it
working on.
The problem I am having is that my wrapper code that compiles and
tests just
fine when using the cc compiler, will not compile under gcc. Here is
the
command line for the cc compile:

cc -c -g -DAIX -qthreaded -D_POSIX_C_SOURCE=199506L -D__EXTENSIONS__
net.c

The command for the gcc compile is (slightly different):

gcc -c -g -DAIX -D_POSIX_C_SOURCE=199506L -D__EXTENSIONS__
-D_XOPEN_SOURCE=5
00L -D_THREAD_SAFE -pthread net.c

After which I get the following errors:
net.c: In function `host_make_by_address':
net.c:141: error: storage size of `he_data' isn't known
net.c:161: error: invalid application of `sizeof' to an incomplete
type
net.c: In function `host_make_by_name':
net.c:203: error: storage size of `he_data' isn't known
net.c:217: error: invalid application of `sizeof' to an incomplete
type
net.c: In function `protocol_make_by_name':
net.c:478: error: storage size of `pr_data' isn't known
net.c:491: error: invalid application of `sizeof' to an incomplete
type
net.c: In function `protocol_make_by_number':
net.c:521: error: storage size of `pr_data' isn't known
net.c:534: error: invalid application of `sizeof' to an incomplete
type
net.c: In function `service_make_by_port':
net.c:627: error: storage size of `sp_data' isn't known
net.c:640: error: invalid application of `sizeof' to an incomplete
type
net.c: In function `service_make_by_name':
net.c:671: error: storage size of `sp_data' isn't known
net.c:684: error: invalid application of `sizeof' to an incomplete
type


A small section of the code (just for the host_make_by_address
function -
and with all the non-relevant ifdefs removed) is here:

================================================== =======================
DLL_EXPORT
host host_make_by_address(const char *address) {
host result = 0;
struct hostent *he = 0;
int addr = 0;

int err_num = 0;
struct hostent he_hold;
struct hostent_data he_data;

addr = inet_addr(address);
if (addr != -1) {
memset(&he_data, 0, sizeof(struct hostent_data));
if (gethostbyaddr_r((char *)&addr, sizeof(addr),
AF_INET,
&he_hold, &he_data) == 0) {
he = &he_hold;
} else {
err_num = errno;
}

if (he) {
result = host_make_from_hostent(he);
} else {
error_set_format(1, 128, "Error in
gethostbyaddr_r:
%d",
err_num);
}
} else {
error_set_format(1, 128, "%s is not a valid IP
address",
address
);
}

return result;
}
================================================== =========================

The main issue is that all of the
struct Xent_data
structures are not seen as being defined when compiling with gcc.

For the life of me, I cannot understand how the cc compiler sees them
as
defined where gcc cannot (especially when the definitions for gcc are
a super-set of the definitions of cc).

Any ideas?

Thanks.

Ravi

[Jeff Trawick]

Ravi Desai wrote:

> The main issue is that all of the
> struct Xent_data
> structures are not seen as being defined when compiling with gcc.
>
> For the life of me, I cannot understand how the cc compiler sees them
> as
> defined where gcc cannot (especially when the definitions for gcc are
> a super-set of the definitions of cc).

gcc uses its own copy of some system header files. Maybe your gcc
installation is using its own netdb.h?

[Ravi Desai]

Jeff Trawick <trawick@attglobal.net> wrote in message news:<uzo9b.11376$ft.7064@twister.southeast.rr.com >...

> Ravi Desai wrote:

> > The main issue is that all of the
> > struct Xent_data
> > structures are not seen as being defined when compiling with gcc.
> >
> > For the life of me, I cannot understand how the cc compiler sees them
> > as
> > defined where gcc cannot (especially when the definitions for gcc are
> > a super-set of the definitions of cc).

>
> gcc uses its own copy of some system header files. Maybe your gcc
> installation is using its own netdb.h?

Thanks for the reply - I've searched (the entire system, actually) for
all netdb.h files. There are no other ones than the one in
/usr/include. It appears that the only #ifdef that could be
interfering with the definition is an #ifdef _ALL_SOURCE.
Unfortunately, setting that flag on results in more issues than I care
to talk about, a _huge_ section of code cannot compile. I'm a bit
flummoxed, really, the cc compiler MUST be setting that flag
internally (unless it has some version of netdb.h buried away
somewhere under a different name). But it somehow is avoiding many of
the other compiler issues that I'm seeing when I use gcc.

I finally gave up and simply copied the structure definitions into my
own file surrounded by a #ifdef __GNUC__ switch. It compiles now, but
large sections of my code fails to pass its unit tests (e.g. condition
variables are not working properly). This same come compiles cleanly
and runs perfectly under cc. Somehow gcc and AIX are not very
compatible it seems.

Have any of you seen this problem?

Thanks,
Ravi