Windows Subsystem for Linux
Memorandum
Bash
The code of line break - EOL i.e., End-of-line - should be LF instead of CRLF in the .profile file on Bash.
I was able to avoid the error with that.

Then type the following command to update.
source .profile

Compiling C source files in GCC on WSL (Ubuntu 64-bit)
You can describe the calling convention by specifying an ABI - i.e., Application Binary Interface - attribute of functions for GCC.

Example
# include <stdarg.h>
signed(__attribute__((ms_abi)) f(signed char **argp,...)) {

EFBFBD
The sequence of three bytes EFh BFh BDh in UTF-8 represents the Unicode Replacement Character U+FFFD.

Remove CRs in a text file with command SED
$ sed -b -i 's/\r//g' FILE

Remove CRs in text files ending in .txt with command FIND and SED
$ find . -type f -name '*.txt' -exec sed -b -i 's/\r//g' {} +;