Be aware of space when issuing HTTP request

Use netcat to issue HTTP request:

# nc -cv https
Connection to 443 port [tcp/https] succeeded!
GET / HTTP/1.1
 Connection: close

HTTP/1.1 400 Bad Request
Content-Length: 54
Content-Type: text/html; charset=UTF-8
Date: Mon, 27 Aug 2018 09:37:22 GMT
Connection: close

<html><title>Error 400 (Bad Request)!!1</title></html>

A superfluous space before “Connection: close” will cause error response. Be aware of it!


Configure Boost.log in CMakeLists.txt on Arch Linux

Today, I tried to build Boost.Log on Arch Linux, but encountered following errors:

undefined reference to `boost::log::v2s_mt_posix::aux::stream_provider<char>::allocate_compound(boost::log::v2s_mt_posix::record&)'
undefined reference to `boost::log::v2s_mt_posix::aux::stream_provider<char>::release_compound(boost::log::v2s_mt_posix::aux::stream_provider<char>::stream_compound*)'
undefined reference to `boost::log::v2s_mt_posix::sources::aux::get_severity_level()'
undefined reference to `boost::log::v2s_mt_posix::aux::unhandled_exception_count()'
undefined reference to `boost::log::v2s_mt_posix::core::open_record(boost::log::v2s_mt_posix::attribute_set const&)'
undefined reference to `boost::log::v2s_mt_posix::core::push_record_move(boost::log::v2s_mt_posix::record&)'
undefined reference to `boost::log::v2s_mt_posix::trivial::logger::get()'
undefined reference to `boost::log::v2s_mt_posix::core::get_logging_enabled() const'
undefined reference to `boost::log::v2s_mt_posix::record_view::public_data::destroy(boost::log::v2s_mt_posix::record_view::public_data const*)'

After some investigation, I find at least on Arch Linux, some modules need to be specified explicitly (E.g., log) while some not (E.g., graph). Besides, I also need claim that I want static library:


Then use Boost_LIBRARIES in linking executable file:



Porting CUDA program from ArchLinux to Ubuntu 16.04

Today I ported a CUDA project from Arch Linux to Ubuntu 16.04, and this post records the pitfalls.

(0) Update cmake to newest version (follow this);

(1) Specify nvcc path in CMakeLists.txt:

SET(CMAKE_CUDA_COMPILER /usr/local/cuda-9.0/bin/nvcc)

otherwise, following error may generate:

No CMAKE_CUDA_COMPILER could be found.

(2) Since Ubuntu 16.04‘s default compiler is still gcc-5, install gcc-6 first, then pass gcc-6 as default compiler for nvcc:

SET(CMAKE_CUDA_FLAGS "-std=c++11 -ccbin gcc-6")

(3) Execute cmake command:


Not Locating CUDA Compiler;
CMake: How to pass mode dependent compile flags to nvcc in visual studio environment;
Tensorflow crashes on build on Ubuntu 16.04 when building for skylake (avx512).


OpenBSD saves me again! — Debug a memory corruption issue

Yesterday, I came across a third-part library issue, which crashes at allocating memory:

Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f594a5a9b6b in _int_malloc () from /usr/lib/
(gdb) bt
#0  0x00007f594a5a9b6b in _int_malloc () from /usr/lib/
#1  0x00007f594a5ab503 in malloc () from /usr/lib/
#2  0x00007f594b13f159 in operator new (sz=5767168) at /build/gcc/src/gcc/libstdc++-v3/libsupc++/

It is obvious that the memory tags are corrupted, but who is the murder? Since the library involves a lot of maths computation, it is not an easy task to grasp the code quickly. So I need to find another way:

(1) Open all warnings during compilation: -Wall. Nothing found.

(2) Use valgrind, but unfortunately, valgrind crashes itself:

valgrind: the 'impossible' happened:
   Killed by fatal signal

host stacktrace:
==43326==    at 0x58053139: get_bszB_as_is (m_mallocfree.c:303)
==43326==    by 0x58053139: get_bszB (m_mallocfree.c:315)
==43326==    by 0x58053139: vgPlain_arena_malloc (m_mallocfree.c:1799)
==43326==    by 0x5800BA84: vgMemCheck_new_block (mc_malloc_wrappers.c:372)
==43326==    by 0x5800BD39: vgMemCheck___builtin_vec_new (mc_malloc_wrappers.c:427)
==43326==    by 0x5809F785: do_client_request (scheduler.c:1866)
==43326==    by 0x5809F785: vgPlain_scheduler (scheduler.c:1433)
==43326==    by 0x580AED50: thread_wrapper (syswrap-linux.c:103)
==43326==    by 0x580AED50: run_a_thread_NORETURN (syswrap-linux.c:156)

sched status:

(3) Change compiler, use clang instead of gcc, and hope it can give me some clues. Still no effect.

(4) Switch Operating System from Linux to OpenBSD, the program crashes again. But this time, it tells me where the memory corruption occurs:

Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x000014b07f01e52d in addMod (r=<error reading variable>, a=4693443247995522, b=28622907746665631,

I figure out the issue quickly, and not bother to understand the whole code. OpenBSD saves me again, thanks!