Category: 黑科技

If you are working with some software which requires you to source some code and messes up with your PATH and other environment variables like Vivado and Merlin compiler, here is a simple and straightforward method to get rid of the mess (to some extent).

#!/bin/bash
VERSION=2016.1
. /space/Xilinx/SDAccel/${VERSION}/settings64.sh
# do something if necessary
if ! test "$0" -ef "$(which $(basename $0))"
then
    exec $(basename $0) "$@"
else
    if test -t 2
    then
        echo "Recursive call detected!" 1&>2
    fi
fi

Some notes:

• Start with #!/bin/bash if you or your script use bash-specific syntax!
• Give this file execution permission with chmod +x!
• Make sure this file itself has the same name as the target program, or is soft-linked to it!
• Use . instead of source, which improves compatibility!

On Linux, if you see

mtr: unable to get raw sockets.

The following might help:

sudo chmod 4755 $(which mtr)

Reference

The reason this happens is that only privileged processes (or processes with proper capabilities(7) on Linux) can create raw sockets, which is needed to send/receive ICMP packets. By chmod(2), the executable will get the S_ISUID mode, which means it can set process effective user ID when execve(2).

A safer solution is

sudo setcap cap_net_raw+ep $(which mtr)

which only gives mtr the cap_net_raw capability.

Reinstalling the mtr package via the package manager should also solve the problem since it will do whatever appropriate to make it work.

According to cplusplus.com, std::vector<bool> in C++ is specialized and consumes only 1/8 space as you may have expected. However, as 8-bit bytes are usually the shortest available type in most implementations, thread-safety is not guaranteed. This could have caused significant trouble in my current project. How lucky I am to notice this interesting feature before I have actually encountered trouble.

Besides, std::bitset provides a fixed size bit array whose length is fixed at compile-time.