Commit Graph

450 Commits

Author SHA1 Message Date
grischka
eadcee6501 macos: yet another tbd adjustment
configure:
- re-enable apple M1-arm64
- however, with --cpu=x86_64,  set -arch in CFLAGS/LDFLAGS too
  (assume rosetta)

Makefile:
- re-enable osx cross-test (Please do not disable tests)

tcc.h
- set TCC_IS_NATIVE for TCC_TARGET_MACHO on __APPLE__
- apply TCC_USING_DOUBLE_FOR_LDOUBLE for x86_64-osx

libtcc.c:
- cleanup tcc_add_file_internal()
- new function char *tcc_load_text(int fd); and use it for tbd files
2021-07-25 20:55:05 +02:00
Sushant Pandurangi
cca4ece0a8 macOS: get active SDK path from xcode-select 2021-07-06 22:48:38 +02:00
Sushant Pandurangi
d5e4b258e1 Minor fixes for gnu90 compatibility 2021-07-06 15:59:12 +02:00
Sushant Pandurangi
f6fb4d0cf1 macOS 11: link using dyld shared cache
Supports linking using .tbd definitions found in the default installed
command-line tools SDK or Xcode.app SDK. Only for creating executables
(not yet for `tcc -run`).
2021-07-04 11:06:55 +02:00
Arthur Williams
ee75521dd5 Support -M, -MM, and -MMD
Add support for some more options to generate dependency fragments.
-M is likes -MD but doesn't compile anything so the command won't fail
when just supplied a file without all the relevant libs.
-MM and -MMD are like their counterparts but skip system libs.

Note the behavior of -MD has changed to include system libs. Use -MMD
for the old behavior. This matches gcc's corresponding flags
2021-07-01 01:44:34 -05:00
grischka
48df89e10e stdatomics: tidy & cleanup
- remove any error messages that were just for debugging the
  templates really
- don't use c99 in tcc (array designators etc.)
- remove memory model type (cannot be an own type really)
  and move memory model defines from built-in to stdatomics.h
- apply normal casts to non-pointer atomic_function arguments
- tidy the library support
- add some tests for errors/warnings

Also:
- Makefile: move GIT_HASH stuff from CFLAGS to DEFINES and into
  main section (away from what is included by tests for example)
- tccelf.c/tccgen.c: avoid some warnings with newer GCC
2021-04-09 10:47:35 +02:00
grischka
72f1dea537 tccelf: use rodata_section, use more rodata in tcc itself
libtcc.c: add -Wwrite-strings to -Wall
tccgen.c: ro float-consts, string-consts, ro arrays if base type is
tccpe.c: merge IAT with rodata
tccrun.c: mprotect rodata accordingly. free section data after copy
x86_64.c: do not use got for static data.
tcc -bench: show data.rw/ro

Probably STB_LOCAL should never get to put_got_entry(), and currently
it doesn't seem to happen (See "Hack Alarm" there)

Other files: use more ro-data in tinycc
2021-02-18 14:43:34 +01:00
grischka
02795106e1 tccelf: use plt-reloc instead of relocplt 2021-02-18 14:42:59 +01:00
herman ten brugge
1c255baad5 test coverage update
Add myself to RELICENSING file
    Use locking when writing tcov file
    Fixed sometimes last line of function not shown
    Merge tcc_tcov_add_file and tcc_add_tcov
    Allow absolute file names
    Count case labels with no code better
2021-01-27 13:27:10 +01:00
Dmitry Selyutin
a110287c31 stdatomic: atomic builtins parsing support 2021-01-26 22:37:44 +03:00
grischka
1ed4b6ba1a debug_modes, re-unalign, cleanups
tccgen.c: debug_modes
- don't waste debug function calls during normal execution.
libtcc.c:
- mem_debug: no C99 features in tcc please, for example
  ({compound expressions}): do not use.
tccgen.c: struct_layout:
- unaligned access is completely ok for most targets.
- Moreover the patch was triggering single byte mode even
  for normal aligned access (as with tcc's SymAttr)

static Sym label: don't do this

arm-gen.c:
- use some #ifdefs to explain some code
tccpp.c:
- cleanup UCN chars
libtcc.c:
- replace openbsd library search
configure:
- cleanup strip fallouts
tccgen.c:
- expr_cond(): remove an exotic optimization that eventually
  got fixed to do the contrary by a gv(RC_InT)
- pop_local_syms(): remove some args
- init_putv() : use write##le functions to avoid cross-compiler
  unaligned access
- __bt_init(): remove unused param 'mode'
2021-01-24 18:00:33 +01:00
herman ten brugge
bc6c0c34c1 implement test coverage
I have implemented the -ftest-coverage option. It works a bit different
from the gcc version. It output .tcov text file which looks almost the
same as a gcov file after a executable/so file is run.

Add lib/tcov.c file
Modify Makefiles to compile/install it
Add -ftest-coverage option in tcc.c/tcc.h/tcc-doc.texi
Add code to tccelf.c/tccgen.c/tccpe.c
Add gen_increment_tcov to tcc.h/*gen.c

unrelated changes:
Add sigemptyset in tccrun.c
Fix riscv64-gen.c tok_alloc label size
2021-01-23 18:17:38 +01:00
herman ten brugge
5aba20f270 BSD: arm support
Support OpenBSD/FreeBSD/NetBSD on asm.

move PAGESIZE to tcc.h and use _SC_PAGESIZE (netbsd/arm has 8192 pagesize)

arm:
- fix cmp instruction for qemu (raspberry pi works without patch?)
- increase start address/size
- use large plt size
- add return R_ARM_PREL31
- add R_ARM_TARGET1 to prepare_dynamic_rel
- add gcc_s to FreeBSD (unwind code)
- do not use __clear_cache on bsd (sometimes bad system call)
- do stack unwinding on bsd
- test/tcctest.c: use %lld %llu on bsd
2021-01-16 07:01:59 +01:00
grischka
bbc7070c82 make test: run cross-test always
To see inconsistencies when they happen.
2021-01-11 15:17:26 +01:00
Christian Jullien
ef7c4388e7 OpenBSD: elfinterp location looks the same for all architectures. i386 WIP 2021-01-10 07:23:03 +01:00
grischka
aeb8f427e2 tccgen: introduce TOK_NEG for unary minus
for floats (currently only).  On x86_64 uses built-in fp
constants (in libtcc1.c) to avoid multiple anonymous
instances.

Also: win32/i386: use __alloca for big struct stack store
- use new function int tok_alloc_const(const char*);
- change alloca86.S to preserve EDX

tccelf.c: fix a warning with 'roinf_use'
2021-01-06 01:44:22 +01:00
CodeHz
425bd2a3db fix "invalid token at start of a preprocessor expression" 2021-01-05 17:46:08 +00:00
Danny Milosavljevic
4a6fb47b8d
arm-asm: Publish g, gen_le16, gen_le32 in tcc.h 2021-01-03 02:34:10 +01:00
grischka
ea82d0826d tccpp: cleanup target-os defines
moved target_machine defines to the <target>-gen.c files.

Also:
- c2str.c moved into conftest.c
- tccdefs.h ; defined(__TINYC__) && !defined(_LOCORE) removed
  (in tinycc __TINYC__ is always defined and _LO... is never.)
- stddef.h : too many #ifdefs, removed
- tccgen.c:stabs: support win32 long doubles aka doubles.
- win32: math.h/tcc_libm.h: fix pointer mismatch in modfl
- tccpp.c: increment include_stack_ptr after the file was
  actually found otherwise it would print
  "in file included from <itself>: file not found..."
2020-12-31 02:03:31 +01:00
herman ten brugge
0821940e26 text relocation for netbsd
netbsd does not allow text relocations in text segment.

tcc.h:
- Add data_ro_section
- Fix typo rela.plt

tccelf.c:
- Add data_ro_section
- Make bounds_section/lbounds_section rw
- Add GNU_RELRO section for data_ro_section/bounds_section/lbounds_section
- Fix relocation for __dso_handle in atexit()

tccgen.c:
- Use data_ro_section

x86_64-gen.c:
- Use R_X86_64_PC32 instead of R_X86_64_64 for bounds checking

tests/Makefile, tests/tests2/Makefile
- Enable dll tests for netbsd
2020-12-30 14:08:06 +01:00
grischka
9f6b65230a include/tccdefs.h: moved and use it
tcc_define_symbol(): now only for -D on command line
include/tccdefs.h: converted to strings and compiled into
the tcc executable.  Can be disabled with
    ./configure --config-predefs=no
In this case include/tccdefs.h is loaded at runtime.  This is
default for other build-methods (build-tcc.bat) also (to avoid
some complexity).

Also:
- lib/Makefile: fix typo
- tcc.h : avoid _strto(u)i64 (for TCC on WIN98/2K)
- tccpp.h:cstr_printf() : workaround incompatible vsnprintf's
  (generally faster too)
2020-12-22 11:06:19 +01:00
herman ten brugge
a87dee588b dlltest_arm
This fixes the dlltest_arm on arm(32)
2020-12-19 20:33:36 +01:00
herman ten brugge
50b4f320dc lazy binding
Currently tcc does not use lazy binding. It puts all relocations in the RELX
section and solve them all at startup.
This was not working on bsd.

tcc.h:
- New RELPLT_SECTION_FMT for plt relocations
- New entry relocplt in struct Section

tccelf.c:
- put_elf_reloca: put R_JMP_SLOT in relocplt section
- build_got_entries*: Use two passes because R_JMP_SLOT and R_GLOB_DAT
                      can not be intermixed on some targets (arm, arm64)
- layout_sections: Calculate correct size relocplt section for DT_ values.
                   Make sure relocplt is last
- fill_dynamic: Add DT_ values when got is filled
                move DT_VERSYM because dynamic linker cannot handle it standone
- Add note section for NetBSD

arm-link.c/arm64-link.c/i386-link.c/riscv64-link.c/x86_64-link.c:
- fill got table with pointer to plt section or symbol value in case
  of TCC_OUTPUT_MEMORY

arm-link.c/arm64-link.c:
- fix offset first plt entry

i386-link.c/x86_64-link.c:
- use correct reloc entry
- use relofs - sizeof (ElfW_Rel) because the reloc is already done

lib/bcheck.c:
- no __libc_freeres on FreeBSD and NetBSD

tests/Makefile:
- Add -fno-stack-protector for OpenBSD

tests/tests2/Makefile:
- disable 106_pthread/114_bound_signal
2020-12-18 15:24:32 +01:00
grischka
e2e62fcb8b replace native platform macros in the compiler
- The compiler should not use these
- However tccrun.c & libtcc1.a files should use these
Also:
- use s1->loaded_dlls for loaded dlls instead of dlopens
- alpine musl: fully supported now and tested
- ./configure ...
   --config-backtrace=no : disable backtraces
   --config-bcheck=no : disable bcheck
- tests:dlltest: enable by default
- tccrun.c : simplify mmaps
- __builtin_alloca : always use asm-alias (instead of #define)
- tccpe.c : use write32le
2020-12-17 12:39:16 +01:00
herman ten brugge
6eef0e35b4 OpenBSD: testcases
Fix all testcases for openbsd except dlltest.

Remember dlopen calls and use them to fix openbsd dlsym problem
Use crtbeginS.o/crtendS.o for DLL for bsd
Do not include -ldl for __NetBSD__
Redirect malloc, realloc, ..., free for bsd
Align stack in tests/asm-c-connect-*.c for x86_64
Remove -B in tests/pp/Makefile (not supported on bsd)
2020-12-16 17:52:59 +01:00
grischka
8ff705554d tcc_enter/exit_state(): do not use!
tcc_enter/exit_state() are meant exclusively to protect
the tcc_compile() and its sub-functions in tccpp.c,
tccgen.c, tccasm.c and xxx-gen.c.

Other files that are part of libtcc simply must not use global
variables.

- riscv64/last_hi: move to TCCState
  from 72250bece2

- tccrun.c: Using a fixed address would not work anyway
  ("tcc -run tcc.c -run ..." for example)
  from baacb0f52a

- tests/Makefile: support for a platform doesn't make sense if
  it doesn't pass our basic tests.
  from 591feda103
Also:
- tccgen: cleanup "duplicate member" (only 2 passes,
  avoids additional TokenSym field)
  from 170be79a42
2020-12-08 19:57:57 +01:00
herman ten brugge
baacb0f52a OpenBSD: runtime fixes
After this commit we can compile and run code with some limitations.
- The dlsym function is broken so this makes -run and bound checking
  not work all the time. Make -k test does work for most code.
- You have to do:
    ln -s /usr/lib/libN.so.x.y /usr/lib/libN.so
  for all .so files in /usr/lib.
  OpenBSD uses opendir/readdir to find the correct so file. This is
  not the way other platforms do this.
  Also the .a versions do not have all symbols that are present in the .so
  files.

tcc.h:
- Use different dynamic loader

elf.h:
- Add SHT_X86_64_UNWIND

tccelf.c:
- Do not use -dl
- Add required NOTE section
- Add extra dynamic tags
- Allow SHT_X86_64_UNWIND/SHT_NOTE in tcc_load_object_file

tccrun.c:
- Uses MAP_FIXED because without the offset between exec and data section
  becomes too big for x86_64

lib/bcheck.c:
- Do not use __libc_freeres

tests/tcctest.c:
- aligned_function also disabled for __GNUC__ == 4
2020-12-07 08:27:10 +01:00
herman ten brugge
170be79a42 duplicate member
Check duplicate struct/union member names

tcc.h: Add cnt field in TokenSym

tccgen.c: New function check_fields to find duplicate member names.

This avoids quadratic behavior and can be used for large structs.
2020-12-03 07:53:44 +01:00
Christian Jullien
4e12c2a6dc OpenBSD: improve partial support for x86_64 - WIP 2020-11-27 11:24:19 +01:00
grischka
cf8d9cf072 win64: fix pe_isafunc()
- tccpe.c: commit "tidy support for helper function" created
  STT_NOTYPE symbols and hence relied on ad-hoc detection which
  didn't work for x86_64 (as reported by Christian Jullien)

- tccgen.c: However to be more safe the helper symbols are
  now made STT_FUNC anyway (via new VT_ASM_FUNC).

Also:
- tcc.h: minor reorder
- riscv64-*, arm64-*, tccmacho.c: avoid some gcc format-warnings
  (mingw-gcc complains about "%llx" being "unknown conversion",
  although it does work since Vista or so)
2020-11-26 16:11:17 +01:00
grischka
4a42b0d95e tidy support for helper function such as memmove
tcc.h, tccgen.c: Introduce Sym *external_helper_sym(int v);
  to create an external reference with no specific type. This
  avoids type conflicts if the symbol is used from C too.
the other files: use it.
2020-11-24 11:47:02 +01:00
grischka
8b69059f66 three small fixes & three reverts
- tcc.h: msvc doesn't grok __func__ (reverts previous commit)

- tccgen.c: fortify tcc against bogus code:
  - n[sizeof({3;})]; // statement expression outside of function
  - f(){"123"4}; // tokens with values following each other
  (also, add "type defaults to int" warning for variables)

- tccpe.c: removed a check that caused BSS symbols not to be
  exported.  Whatever that check was meant to prevent.

- win32/build-tcc.bat: cmd.exe sometimes doesn't grok '-' in labels

- Revert "libtcc: no need to undef"
  This reverts commit 2b7aa2a1e1.
- Revert "tcc.h libtcc.c: remove unused defines"
  This reverts commit 985d963745.

The point of these "unused defines" is to be unused,  that is
to remind people not to use malloc but please to "use_tcc_malloc",
instead.
2020-11-02 18:08:56 +01:00
Kyryl Melekhin
985d963745 tcc.h libtcc.c: remove unused defines
pretty sure that functions with use_* do not exist
and attempts to use the macros will fail to link
I could rename them to be more up to date like tcc_malloc,
but to me overloading the std calls with macros is
probably taking away control from the programmer,
so for the best is to just get rid of them.
2020-11-01 15:24:45 +00:00
John Scott
53587ee415
tcc_internal_error: print function with __func__.
Though __func__ was introduced in C99, this is
preferable to __FUNCTION__, an obsolete GCC extension.
Found with gcc -Wpedantic.
2020-10-18 17:54:01 -04:00
grischka
72b520e709 tccgen: flex arrays etc.
Fixes potential writes past the allocated space with mostly
illegal flex array initializers. (60_errors_and_warnings.c
:test_var_array)

In exchange suspicious precautions such as section_reserve
or checks with sec->data_allocated were removed.  (There is
an hard check 'init_assert()' for now but it's meant to be
just temporary)

Also, instead of filling holes, always memset(0) structures
& arrays on stack.  Sometimes more efficient, sometimes isn't.
At least we can omit putting null initializers.

About array range inititializers:  Reparsing tokens has a
small problem with sideeffects, for example

   int c = 0, dd[] = { [0 ... 1] = ++c, [2 ... 3] = ++c };

Also, instead of 'squeeze_multi_relocs()', delete pre-existing
relocations in advance. This works even if secondary initializers
don't even have relocations, as with
    [0 ... 7] = &stuff,
    [4] = NULL

Also, in tcc.h: new macro "tcc_internal_error()"
2020-10-03 18:12:46 +02:00
grischka
cdc3df949b tcc -bench: show text/data/bss binary output sizes 2020-10-02 19:50:45 +02:00
Michael Matz
352e1d0fc4 Reinstate attribute alias handling
commit 2a0167a merged alias and asm symbol renaming, but broke
semantics of aliases, see testcase.  Basically the difference between
the two is that an asm rename doesn't generate a new symbol, i.e. with

  int foo __asm__("bar");

all source reference to 'foo' will be to 'bar', nothing of the name
'foo' will remain in the object file, and for instance reference to
'foo' from other compilation units won't be resolved to this one.

Aliases OTOH create an additional symbol.  With:

  void target (void) { return; }
  void afunc (void) __attribute__((alias("target")));

reference to 'afunc' will remain 'afunc' in the object file.  It will
generate two symbols, 'afunc' and 'target' referring to the same entity.
This difference matters if other compilation units make references to
'afunc'.

A side requirement of this is that for alias to work that the target
symbol needs to be defined in the same unit.  For TCC we even require a
stricter variant: it must be defined before the alias is created.

Now, with this I merely re-instated the old flow of events before above
commit.  It didn't seem useful anymore to place both names in the
asm_label member of attributes, and the asm_label member of Sym now
again only needs the hold the __asm__ rename.

It also follows that tcc_predefs.h can't make use of attribute alias to
e.g. map __builtin_memcpy to __bound_memcpy (simply because the latter
isn't defined in all units), but rather must use __asm__ renaming, which
in turn means that the underscore handling needs to be done by hand.
2020-09-30 17:46:01 +02:00
Pursuer2
8878c29c5d misplaced parenthese around definition of CONFIG_TCC_BCHECK 2020-09-12 07:09:18 +02:00
grischka
f9870f7860 bcheck: remove static (compile-time) control
Providing both run-time and compile-time control for bounds
checking as an user interface appears unnecessary and confusing.

Also:
- replace 'bound_...' by 'bounds_...' for consistency
- tcc-doc: put related info into one place and cleanup

The __bounds_checking(x) function is still missing explanation.
(I.e. what happens if the accumulated value drops below zero.)
2020-08-21 20:26:36 +02:00
herman ten brugge
50fe33f880 Add attribute bound_no_checking
tcc-doc.texi:
- Document attribute bound_no_checking

tcctok.h:
- Add bound_no_checking attribute

tcc.h:
- Add no_bcheck function attribute

tccgen.c:
- Use function attribute no_bcheck in merge_funcattr/parse_attribute/gen_function

bcheck.c:
- Fix no_checking in __bound_new_region/__bound_free/__bound_check

tests/tests2/114_bound_signal.c:
- Fix code with new attribute bound_no_checking

tests/tests2/103_implicit_memmove.c:
- Fix memmove prototype
2020-08-13 11:19:11 +02:00
herman ten brugge
c1e1c17c0a Move bound functions to tccgen.c
Move gen_bounded_ptr_add() and gen_bounded_ptr_deref() code to tccgen.c
No functional changes.
2020-07-12 10:55:40 +02:00
Michael Matz
40671f76e4 Fix parsing of .s files
those aren't preprocessed, but our use of a fake file in
preprocess_start requires inline stack processing (which isn't done
without preprocessing).  Just don't try to setup anything requiring
preprocessing at all in this case.
2020-07-06 18:12:35 +02:00
grischka
2a0167adfe __builtin_/__bound_: A 'stay tiny' approach to the matter
tccgen.c:
- cleanup __builtin_... stuff
- merge __attribute((alias("sym"))) with __asm__("sym")
    Now one cannot have both, however for alias underscores are
    added if enabled.  For __asm__ they aren't.
tccpp.c:
- extend tcc_predefs accordingly.  Was generated with
  'cd tests/misc && tcc -run c2str.c tcc_predef.h tcc_predefs'
xxx-gen.c:
- move bcheck setjmp test to tccgen.c:gbound_args()
i386-gen.c:
- create win32 compatible stack space for big structures
tcctest.c:
- some cleanup + nicer output
2020-07-06 13:42:02 +02:00
grischka
6a4f3cf127 rework leading underscores
tested on win32/64 to pass the tests when enabled

- libtcc.c :
  let tcc define __leading_underscore if enabled
  tcc_add_symbol() : add _ automatically
- tccelf.c : remove tcc_get_symbol_err(), find_c_sym()
  currently symbol length is limited to 256 in several
  places, so we can use a fixed local buffer for now as well.
- win32/lib/crtinit.c : new file for init/fini
- lib/*.S, tests7* : use __leading_underscore
- bt-log.c: this file wont work relibaly if compiled with gcc
2020-07-06 13:00:47 +02:00
Michael Matz
c86760c1e9 macos: Read exported symbols from dylibs
up to now we simply assumed that any undefined symbols will be
provided by some shared libs on the cmdline.  Now we check this.
2020-06-20 22:17:08 +02:00
Michael Matz
4eff2b5f6a macos: more adjustments for OSX systems
* instead of /usr/include use the current SDK path as system
  include directory (/usr/include is empty with current tools)
  (this also removes the need to add these paths in individual
  Makefiles)
* define _DARWIN_C_SOURCE in tcc.h to get the full set of decls
  from system headers (e.g. vsnprintf), similar to _GNU_SOURCE
  (and don't define _ANSI_SOURCE in the main Makefile anymore)
* tests/tests2/Makefile: remove the -w flag, it's added when necessary
  in the rules generating the .expect files
2020-06-20 22:17:06 +02:00
Michael Matz
f18f865159 Handle always_inline as GNU inline
this is needed for multi-file testcases using stdio.h, as
the __sputc function is implemented as a extern inline
function (with gnu_inline attribute, but we don't support that for now).

Without this change that leads to multiply defined symbols when using
multiple units including stdio.h.

It also has an always_inline attribute, which we can use to guide our
behaviour, as in ISO-C an always_inline can't be defined with ISO
'extern inline' semantics.  This is the minimal change and not a full
implementation of GNU inline semantics, which would require thorough
testcases.

If __clang__ would be defined the header would make use of C99 semantics,
which would work for us.  It would also do that if _GNUC_ wouldn't be
defined.  But we can't do the latter (as the whole MacOSX SDK refuses
to be compiled with anything not defining that).  I haven't tested
defining __clang__, but suspect that's going to be problematic.
2020-06-20 22:14:56 +02:00
Michael Matz
71b0634168 Add find_c_sym and friends
for handling leading underscores when looking up symbols.
Necessary on MacOS, as there C symbols have a '_' prepended.
get_sym_addr (replacing get_elf_sym_addr) gets an argument to
specify if bare/raw/ELF symbols should be looked up or if decorated
C symbols should be looked up.  That reflects into tcc_get_symbol.
tcc_add_symbol is _not_ yet changed, but probably should be.
2020-06-20 22:12:02 +02:00
Michael Matz
bbccb13566 for_each_element for all; add tcc_exit_state
this moves the for_each_element macro to tcc.h and adds a
tcc_exit_state (and uses it) pairing with tcc_enter_state.
2020-06-20 22:11:57 +02:00
Michael Matz
94066765ed macos: First cut at generating Mach-O executables
this does generate a working executable for a very simple
example input, e.g. this:

% cat simple.c
int main(void)
{
  return 0;
}
% ./tcc -B. -c simple.c
% ./tcc -nostdlib -B. simple.o -lc
% ./a.out && echo okay
okay

(the -lc is actually not necessary right now, see below).  This
has many limitations:

* no symbol table, hence no calls to external functions from
  e.g. libc, aka libSystemB
* no proper entry point (should be main, but is hardcoded to first
  real .text address)
* libSystemB is hardcoded, no other libs are supported (but again
  no external calls anyway)
* generated Mach-O executable is in old format: neither LC_DYLD_INFO
  no export tries for symbols are created (no symbol table at all!)
* the __LINKEDIT segment is faked and empty, as dyld doesn't like
  it empty even if no symbols point into it
* same with __DATA, dyld wants a non-empty writable segment which
  we enforce with useless data
* no relocations, hence no function call stubs (lazy or not) are
  generated
* hardcodes some other constants as well
2020-06-20 22:09:21 +02:00