Enable newlib building

[mskvortsov]

git clone git://sourceware.org/git/newlib-cygwin.git
export CC_FOR_TARGET=<path-to-clang>
export PATH=<path-to-binutils-gdb>:$PATH
configure --target=msp430-elf
make

[mskvortsov]

Current workarounds:

diff --git a/newlib/configure.host b/newlib/configure.host
index 9e809c9a8..de704a7d6 100644
--- a/newlib/configure.host
+++ b/newlib/configure.host
@@ -256,8 +256,7 @@ case "${host_cpu}" in
   msp430*)
        newlib_cflags="${newlib_cflags} -DPREFER_SIZE_OVER_SPEED -DSMALL_MEMORY"
        newlib_cflags="${newlib_cflags} -ffunction-sections -fdata-sections "
-       newlib_cflags="${newlib_cflags} -mOs "
-       newlib_cflags="${newlib_cflags} -mhwmult=none "
+       newlib_cflags="${newlib_cflags} -Wno-unused-command-line-argument "
        machine_dir=msp430
        default_newlib_nano_malloc="yes"
        ;;
diff --git a/newlib/libc/include/limits.h b/newlib/libc/include/limits.h
index 893f10834..c32ac9302 100644
--- a/newlib/libc/include/limits.h
+++ b/newlib/libc/include/limits.h
@@ -129,7 +129,11 @@
 
 #if defined __GNUC__ && !defined _GCC_LIMITS_H_
 /* `_GCC_LIMITS_H_' is what GCC's file defines.  */
-# include_next <limits.h>
+#  define UINT_MAX 65536
+#  define INT_MAX  32767
+#  define CHAR_MAX 127
+#  define CHAR_BIT 8
+#  define LONG_MAX 2147483647L
 #endif /* __GNUC__ && !_GCC_LIMITS_H_ */
 
 #ifndef _POSIX2_RE_DUP_MAX

[mskvortsov]

Issues #9, #10 are related. Also, at least __builtin_flt_rounds should be implemented to fix

newlib/libc/stdlib/strtod.c:490:6: error: cannot compile this builtin function yet

[asl]

What does -mOS mean? I guess the first patch would go away after we will merge #5 ?

Why the limits.h do not work?

[mskvortsov]

limits.h comes from host for some reason.

[mskvortsov]

$ msp430-gcc-7.3.1.24_linux64/bin/msp430-elf-gcc --help=target
The following options are target specific:
  -mOs                        This option lacks documentation.
  ...

This is fun. My guess it's -Osize.

[asl]

limits.h comes from host for some reason.

Ah, ok. Probably something for @chbessonova to look for as well.

[chbessonova]

Regarding -m0s:

     /* This is a hack to work around a problem with the newlib build
     mechanism.  Newlib always appends CFLAGS to the end of the GCC
     command line and always sets -O2 in CFLAGS.  Thus it is not
     possible to build newlib with -Os enabled.  Until now...  */
  if (TARGET_OPT_SPACE && optimize < 3) 
    optimize_size = 1; 

[chbessonova]

Regarding limits.h.
Looks like the system 'limits.h' is included by clang's 'build/lib/clang/8.0.0/include/limits.h' since __STDC_HOSTED__ is defined by default.
It could be resolved by setting __STDC_HOSTED__ to 0 using -ffreestanding option:

export CC_FOR_TARGET=<path_to_clang> -ffreestanding

[asl]

Looks like the system 'limits.h' is included by clang's 'build/lib/clang/8.0.0/include/limits.h' since STDC_HOSTED is defined by default.

Then something is wrong with the paths we're providing. Does newlib provide limits.h? As far as I can see, yes (https://github.com/eblot/newlib/blob/master/newlib/libc/include/limits.h). So we should pick this instead of the system one,

[chbessonova]

@asl This issue comes from this newlib provided '../newlib/libc/include/limits.h'. It '#next_include's another 'limits.h' which is supposed to be a compiler-specific. In case of gcc toolchain, the compiler includes its specific header and the chain of 'limits.h' includes stops.
But clang doesn't stop by including clang-specific 'limits.h'. It tries to '#next_include' another (3rd one) 'limits.h' which is taken from system headers (no other left).

[asl]

Then something is wrong with the defines, etc. So, it should be investigated. -ffreestanding is not an option since we're doing hosted toolchain :)

[asl]

There is also a special kludge there, see:

/* The system's limits.h may, in turn, try to #include_next GCC's limits.h.
    Avert this #include_next madness. */
 #if defined __GNUC__ && !defined _GCC_LIMITS_H_
 #define _GCC_LIMITS_H_
 #endif

So, it seems we'd need something similar to newlib.

[chbessonova]

In the same file by two lines below:

/* System headers include a number of constants from POSIX in <limits.h>.
   Include it if we're hosted. */
#if __STDC_HOSTED__ && __has_include_next(<limits.h>)
#include_next <limits.h>
#endif

What 'another' limits.h is supposed to be included here, if not a system one?

Added:
Looks like I got what should be done to resolve the issue properly.

[chbessonova]

Updated #5 with a fix for the 'limits.h' issue.
Please, take a look.

[chbessonova]

• .refsym directive is not supported (see .refsym directive is not supported #29)

../../.././libgloss/msp430/crt0.S:58:2: error: unknown directive
 .refsym __crt0_call_init_then_main
 ^

• CALLn is not supported (see [MCLayer] Add remaining instruction forms #7)

../../.././libgloss/msp430/crt0.S:249:7: error: invalid operand for instruction
 CALL @R7