Declarator for inline and undeclared identifier messages

When researching a difference between the current versions of libarchive on AIX and trying to figure out why the libarchive.so wasn’t being symlinked to what was being built, I got the following compilation error on the release package for v3.4.3:

"libarchive/archive_endian.h", line 158.8: 1506-485 (S) Parameter declaration list is incompatible with declarator for inline.
"libarchive/archive_endian.h", line 170.45: 1506-045 (S) Undeclared identifier pp.
"libarchive/archive_endian.h", line 172.16: 1506-045 (S) Undeclared identifier u.
"libarchive/archive_endian.h", line 178.1: 1506-277 (S) Syntax error: possible missing ';' or ','?

Undeclared identifier? It’s right there!

The “undeclared identifier” messages are confusing, because, at first glance, it appears that the identifier is defined in the parameter list.

static inline void
archive_be64enc(void *pp, uint64_t u)
{
	unsigned char *p = (unsigned char *)pp;

	archive_be32enc(p, (uint32_t)(u >> 32));
	archive_be32enc(p + 4, (uint32_t)(u & 0xffffffff));
}

IBM forum result didn’t seem all that helpful

Searching for what might actually lead to the the error “Parameter declaration list is incompatible with declarator for inline” led to XLC complains CCN3277, CCN3485, CCN3045 but gcc on z/Linux does not complain with the seemingly unhelpful response, “Then what gcc (or MS, for that matter) does is irrelevant. You have to take these errors one at a time and resolve them.”

Wait… inline is… C++?

inline is a keyword in C++, not C, but gcc supports inline as well, leading to a departure from the C89 standard. Curiously, v3.6.2 of libarchive fixes this error, so all I needed to do is figure out how they’re compiling differently (I hoped).

Diff all the things!

I downloaded the v3.4.3 and v3.6.2 releases of libarchive and ran the ./configure script for both of them, and then did a diff on the generated Makefile and libtool. Doing so showed that v3.4.3 was using cc -qlanglvl=extc89 to invoke the C compiler while v3.6.2 was using cc -qlanglvl=extc1x … extc1x pointing to a 201x C standard instead of C89 for the AIX xLC compiler.

Solution

The solution was to replace all occurrences of extc89 with extc1x to get past this error. Makefile and libtool had two lines each in my case. The undeclared identifier error is a result of the misinterpretation of the inline syntax. Once I resolved the inline issue, the C function header was interpreted correctly.

pthread error

Working with open source projects on AIX is challenging due many factors, including lack of access to development environments for AIX, semi-closed forums, and lack of open documentation stemming from the closed and proprietary environments. I still have a subsequent error to deal with my build of libarchive:

ld: 0711-317 ERROR: Undefined symbol: .pthread_mutex_lock
ld: 0711-317 ERROR: Undefined symbol: .pthread_mutex_unlock
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.

The above .pthread_mutex errors can be resolved by making sure -lpthread is in the LIBS variable for the generated Makefile, which is ultimately sources from build/pkgconfig/libarchive.pc in the case of libarchive

More to come

Building the last version of libarchive (3.4.0) that worked for a release on AIX results in a new error: 1506-285 (S) The indirection operator cannot be applied to a pointer to an incomplete struct or union. This will be my next build error to tackle, or at least see why this version is specifically