Add support for init/fini arrays to libc

[akosthekiss]

The arrays contain the addresses of functions annotated with
constructor or destructor attributes. The support is optional,
requires FEATURE_INIT_FINI cmake option to be set. As of now, the
option is not available in tools/build.py directly, only via
--cmake-param="-DFEATURE_INIT_FINI=ON".

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss [email protected]

[akosthekiss]

This patch is a proposed solution for #1722.

The constructor/destructor behavior can be tested, e.g., by adding the below two functions anywhere in the compiled sources. (For my experiments, I've copied them into jerry-main/main-unix.c.)

static void __attribute__ ((constructor))
start_jerry (void)
{
  printf ("JERRY STARTED\n");
}

static void __attribute__ ((destructor))
finish_jerry (void)
{
  printf ("JERRY FINISHED\n");
}

If configured properly, start_jerry and finish_jerry will be invoked even though they are not called anywhere explicitly. First example on ARM32.

$ ./tools/build.py --clean --cmake-param="-DFEATURE_INIT_FINI=ON" --toolchain cmake/toolchain_linux_armv7l.cmake
$ file ./build/bin/jerry
./build/bin/jerry: ELF 32-bit LSB  executable, ARM, EABI5 version 1 (SYSV), statically linked, BuildID[sha1]=5863cc6fdcdcf956d6910a266f7ce583fd20c995, stripped
$ qemu-arm-static ./build/bin/jerry ./tests/hello.js
JERRY STARTED
Hello JerryScript!
JERRY FINISHED

It also works on x86-64:

$ ./tools/build.py --clean --cmake-param="-DFEATURE_INIT_FINI=ON"
$ file ./build/bin/jerry 
./build/bin/jerry: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=73dba6c37fed7aa9aea19b533e76f1d2bfcf28e2, stripped
$ ./build/bin/jerry ./tests/hello.js 
JERRY STARTED
Hello JerryScript!
JERRY FINISHED

Sanity check: if the feature is not enabled in jerry-libc, the constructors/destructors don't run.

$ ./tools/build.py --clean
$ ./build/bin/jerry ./tests/hello.js
Hello JerryScript!

Note 1: Haven't tested on x86.

Note 2: Had to modify cppcheck suppression list, as cppcheck incorrectly reported void * arithmetics. Actually, arithmetics is performed on function pointers for which the return type is void, but that should be a completely different story, IMHO.

jerry-libc/jerry-libc-init.c:62: portability(arithOperationsOnVoidPointer): '__preinit_array_end' is of type 'void *'. When using void pointers in calculations, the behaviour is undefined.

[akosthekiss]

An additional sanity check: the enhanced jerry-libc works just like the system libc (which needs no extra feature switches, of course).

$ ./tools/build.py --clean --jerry-libc=off --jerry-libm=off --static-link=off --link-lib="-lm"
$ file ./build/bin/jerry 
./build/bin/jerry: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=138ef44c61b06bb6fe7f5b0b36be1994b6b4d2c0, stripped
$ ./build/bin/jerry ./tests/hello.js 
JERRY STARTED
Hello JerryScript!
JERRY FINISHED

[gabrielschulhof]

Super-awesome 🎉

[zherczeg]

LGTM

[zherczeg]

The function header comment is different for libc functions?

[akosthekiss]

I might have been sloppy. Will get it right asap.

[akosthekiss]

I've fixed the function doc comments in the new file and updated the commit.

[LaszloLango]

LGTM