gcc-8 on Linux doesn't like usage of strncat :
`warning: ‘strncat’ output truncated before terminating nul copying as many bytes from a string as its length`.
Not sure what was wrong, it might be a false positive,
but the logic is simple enough to replaced by a simple `memcpy()`,
thus avoiding the shenanigans of null-terminated strings.
following #1356,
only enable backtrace compilation on linux+glibc.
Also, disable backtrace by default from "release" compilation,
so that less platforms get impacted by the new requirements.
Can be manually enabled/disabled using BACKTRACE=1/0.
note : for some reason,
scan-build version on my laptop found problems within fastcover.c
that scan-build on travisCI does not flag.
They are, as usual, false positive :
the analyzer does not understand that a table (`offset`) is correctly filled before usage.
from EXIT_IF() to RETURN_IF()
EXIT could be misunderstood as exit(), which terminates program execution.
But the macro only leaves the function, not the program.
For OSX and Linux, add a signal handler to SIGABRT, SGIFPE, SIGILL,
SIGSEGV, and SIGBUS. When the program terminates unexpectedly the
handler will print the current stack to the terminal to help determine
the location of the failure.
On OSX the output will look like:
```
Stack trace:
4 zstd 0x000000010927ed96 main + 16886
5 libdyld.dylib 0x00007fff767d1015 start + 1
6 ??? 0x0000000000000001 0x0 + 1
```
On Linux the output will look like:
```
Stack trace:
./zstd() [0x4b8e1b]
./zstd() [0x4b928a]
./zstd() [0x403dc2]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f5e0fbb0445]
./zstd() [0x405754]
```
As is, the code does not function on WIN32.
See also: https://oroboro.com/stack-trace-on-crash/
Per warnings from flawfinder: "Does not check for buffer overflows when
copying to destination [MS-banned] (CWE-120). Consider using snprintf,
strcpy_s, or strlcpy (warning: strncpy easily misused).".
Replaced called to strcpy and strcat in `fileio.c` to calls with a
specified size (`strncpy` and `strncat`).
Tested the changes on OSX, Linux, Windows.
On OSX + Linux, changes were tested with ASAN. The following flags were
used: 'check_initialization_order=1:strict_init_order=1:detect_odr_violation=1:detect_stack_use_after_return=1'
To reproduce warning:
./flawfinder.py ./programs/fileio.c
tells in a non-blocking way if there is something ready to flush right now.
only works with multi-threading for the time being.
Useful to know if flush speed will be limited by lack of production.
