Build ROHC library with tcc

[Didier Barvaux]

It would be great if the ROHC library could be built with the tcc compiler.

[Didier Barvaux (didier-barvaux)]

The problem was reported to tinycc developers: http://lists.gnu.org/archive/html/tinycc-devel/2011-04/msg00015.html
The problem is fixed upstream, but no official release contains the fix.

[Didier Barvaux (didier-barvaux)]

How to install git version of tinycc:
$ git clone git://repo.or.cz/tinycc.git
$cd tinycc
$ ./configure --prefix=/tmp/tcc --cc=gcc --cpu=x86
$ make
$ make install
$ /tmp/tcc/bin/tcc -v
tcc version 0.9.25

[Didier Barvaux (didier-barvaux)]

Trying to build the library with git version of tcc:

$ CC=/tmp/tcc/bin/tcc LD=/tmp/tcc/bin/tcc ./autogen.sh
[everything's fine]
$ make CC=/tmp/tcc/bin/tcc LD=/tmp/tcc/bin/tcc clean all
[everything's fine, cool!]
$ make CC=/tmp/tcc/bin/tcc LD=/tmp/tcc/bin/tcc check
[...]
make check-TESTS
make[4]: Entering directory `<path>/rohc-main/test/robustness/empty_payload'
FAIL: test_empty_payload_ir.sh
FAIL: test_empty_payload_irdyn.sh
FAIL: test_empty_payload_uo0.sh
FAIL: test_empty_payload_uo0_iponlyprofile.sh
FAIL: test_empty_payload_uo0_udpprofile.sh
FAIL: test_empty_payload_uo1.sh
FAIL: test_empty_payload_uor2.sh
===========================================
7 of 7 tests failed
Please report to http://launchpad.net/rohc/
===========================================
make[4]: *** [check-TESTS] Error 1
make[4]: Leaving directory `<path>/rohc-main/test/robustness/empty_payload'
make[3]: *** [check-am] Error 2
make[3]: Leaving directory `<path>/rohc-main/test/robustness/empty_payload'
make[2]: *** [check-recursive] Error 1
make[2]: Leaving directory `<path>/rohc-main/test/robustness'
make[1]: *** [check-recursive] Error 1
make[1]: Leaving directory `<path>/rohc-main/test'
make: *** [check-recursive] Error 1

$ ./test/robustness/empty_payload/test_empty_payload_ir.sh verbose verbose
[rohc_comp.c:147 rohc_alloc_compressor()] creating compressor
[rohc_comp.c:1519 c_alloc_contexts()] enlarge the context array from 0 to 4 elements (MAX_CID = 15)
enable all compression profiles
packet #1:
 packet is valid
[ip.c:77 ip_create()] bad IP header size (20 bytes)
[ERROR] [rohc_comp.c:349 rohc_compress()] cannot create the outer IP header
 failed to compress IP packet
[rohc_comp.c:243 rohc_free_compressor()] free contexts
[rohc_comp.c:247 rohc_free_compressor()] free feedback buffer

[Didier Barvaux (didier-barvaux)]

Problem seems related to the lengths of bit-fields in the iphdr struct defined by netinet/ip.h.

Question asked to the tinycc ML: http://lists.gnu.org/archive/html/tinycc-devel/2012-05/msg00019.html

[Didier Barvaux (didier-barvaux)]

Revision 370 adds a configure check for bit-fields lengths. This way compilers that will generates unexpected code for the library are detected earlier.

$ CC=/tmp/tcc/bin/tcc LD=/tmp/tcc/bin/tcc ./autogen.sh
[...]
checking whether the compiler computes bit-field lengths as expected... no
configure: error: in `/home/didier/documents/tech/dev/rohc/rohc-main':
configure: error: The compiler does not behave as expect for bit-field lengths, it would break the library
See `config.log' for more details

$ CC=gcc LD=gcc ./autogen.sh
[...]
checking whether the compiler computes bit-field lengths as expected... yes
[...]

$ CC=clang LD=clang ./autogen.sh
[...]
checking whether the compiler computes bit-field lengths as expected... yes
[...]

[Didier Barvaux (didier-barvaux)]

Attach patch for TCC in order to pack bit fields the way GCC does.

[Didier Barvaux (didier-barvaux)]

With the attached patch for TCC, some warnings were encountered in the library and the non-regression tests segfault. The warnings were easy to fix (see http://bazaar.launchpad.net/~didier-barvaux/rohc/main/revision/530) but the segfaults are caused by a bug in TCC (see http://lists.nongnu.org/archive/html/tinycc-devel/2012-10/msg00029.html).

[Didier Barvaux (didier-barvaux)]

Attached patch was proposed upstream. See http://lists.nongnu.org/archive/html/tinycc-devel/2012-10/msg00030.html

[Didier Barvaux (didier-barvaux)]

Re-schedule for 1.6.0 since upstreams bugs will (probably) not be fixed soon.

[Didier Barvaux (didier-barvaux)]

Not really a bugfix. The ROHC library has no strong requirement on bitfields anymore (struct iphdr embedded for MinGW/FreeBSD builds, then modified to use uint8_t instead of unsigned int for MinGW 4.7), so the configure check is now useless and TCC builds the library fine.

See http://bazaar.launchpad.net/~didier-barvaux/rohc/main/revision/629 for main branch.
See http://bazaar.launchpad.net/~didier-barvaux/rohc/1.5.x/revision/552 for 1.5.x branch.