_GNU_SOURCE not defined on Debian/Ubuntu (was: c99 does not define getaddrinfo())

[vincentbernat]

Hi!

When compiling on Debian, I get the following error:

pxyconn.c: In function ‘pxy_sni_resolve_cb’:
pxyconn.c:1524:23: error: dereferencing pointer to incomplete type
pxyconn.c:1524:36: error: dereferencing pointer to incomplete type
pxyconn.c:1525:19: error: dereferencing pointer to incomplete type
pxyconn.c: In function ‘pxy_fd_readcb’:
pxyconn.c:1605:19: error: storage size of ‘hints’ isn’t known
pxyconn.c:1605:19: warning: unused variable ‘hints’ [-Wunused-variable]

The problem is that getaddrinfo() is a POSIX.1g extension and is not available in pure C99. It may work if libevent has also been compiled with --std=c99 because struct evutil_addrinfo will be defined as a full structure. Otherwise, it is just an alias to struct addrinfo which is not defined in netdb.h but still exists as an incomplete type in event2/utils.h.

You can either compile with --std=gnu99 or with -D_POSIX_C_SOURCE=200112L. With the later option, there are additional errors later. Moreover, compiling with --std=gnu99 almost silents out any warnings. I don't know if such a standard is portable outside of gcc.

[droe]

-D_GNU_SOURCE is supposed to get added to CPPFLAGS automatically when building on a glibc system, which in turn should pull in getaddrinfo() and all the other definitions not in C99 and silence all warnings. SSLsplit is definitely supposed to build warning-free, given recent enough OpenSSL headers. I suspect the auto-detection is not good enough. Can you check the following:

• Does the GCC invocation line just before the errors contain -D_GNU_SOURCE?
• Does /usr/include/gnu/libc-version.h exist on your system?
• Does it build when you run make like this: CPPFLAGS=-D_GNU_SOURCE make?

[vincentbernat]

Here is the line used:

cc -c   -DDISABLE_SSLV2_SESSION_CACHE -DHAVE_NETFILTER -D"BNAME=\"sslsplit\"" -D"PNAME=\"SSLsplit\"" -D"VERSION=\"0.4.4\"" -D"FEATURES=\"-DDISABLE_SSLV2_SESSION_CACHE -DHAVE_NETFILTER\"" -D"BUILD_DATE=\"2012-05-13\"" -g   -pthread -std=c99 -Wall -Wextra -pedantic -D_FORTIFY_SOURCE=2 -o pxyconn.o pxyconn.c

I have no /usr/include/gnu/libc-version.h but I have a /usr/include/x86_64-linux-gnu/gnu/libc-version.h. This is a change to support multiarch. This should be the same with recent versions of Ubuntu.

And yes, it works fine with CPPFLAGS=-D_GNU_SOURCE make.

Maybe you can grab default search path from gcc with gcc -v -E - < /dev/null.

[droe]

Fixed in latest master. Thank you for reporting the issue.