[Gm2] Build failure on Lubuntu building gm2 on top of gcc trunc (8.0.0)

[Christoph Schlegel]

Hello Gaius,

happy new year! Here is where the build stops on
Linux christoph-VGN-N21S-W 4.13.0-25-generic #29-Ubuntu SMP Mon Jan 8 21:13:33 
UTC 2018 i686 i686 i686 GNU/Linux:

g++ -fno-PIE -c -g -I-I../../gcc-8.0.0/gcc/gm2 -Igm2 
-I../../gcc-8.0.0/gcc/gm2/gm2-gcc -Igm2/gm2-gcc    -DIN_GCC     -fno-exceptions 
-fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings 
-Wcast-qual  -fno-common  -DHAVE_CONFIG_H -I. -Igm2 -I../../gcc-8.0.0/gcc 
-I../../gcc-8.0.0/gcc/gm2 -I../../gcc-8.0.0/gcc/../include 
-I../../gcc-8.0.0/gcc/../libcpp/include  -I../../gcc-8.0.0/gcc/../libdecnumber 
-I../../gcc-8.0.0/gcc/../libdecnumber/bid -I../libdecnumber 
-I../../gcc-8.0.0/gcc/../libbacktrace   -I. -Igm2 -I../../gcc-8.0.0/gcc 
-I../../gcc-8.0.0/gcc/gm2 -I../../gcc-8.0.0/gcc/../include 
-I../../gcc-8.0.0/gcc/../libcpp/include  -I../../gcc-8.0.0/gcc/../libdecnumber 
-I../../gcc-8.0.0/gcc/../libdecnumber/bid -I../libdecnumber 
-I../../gcc-8.0.0/gcc/../libbacktrace  ../../gcc-8.0.0/gcc/gm2/gm2-lang.c -o 
gm2/gm2-lang.o
../../gcc-8.0.0/gcc/gm2/gm2-lang.c: In function 'tree_node* 
gm2_langhook_type_for_mode(machine_mode, int)':
../../gcc-8.0.0/gcc/gm2/gm2-lang.c:509:73: error: cannot convert 'poly_uint16 
{aka poly_int<1, short unsigned int>}' to 'unsigned int' for argument '1' to 
'tree_node* gm2_langhook_type_for_size(unsigned int, int)'
     return gm2_langhook_type_for_size (GET_MODE_BITSIZE(mode), unsignedp);
                                                                         ^
../../gcc-8.0.0/gcc/gm2/gm2-lang.c:512:38: error: switch quantity not an integer
       switch (GET_MODE_BITSIZE (mode))
                                      ^
../../gcc-8.0.0/gcc/gm2/gm2-lang.c:527:38: error: switch quantity not an integer
       switch (GET_MODE_BITSIZE (mode))
                                      ^
../../gcc-8.0.0/gcc/gm2/gm2-lang.c: In function 'bool 
gm2_mark_addressable(tree)':
../../gcc-8.0.0/gcc/gm2/gm2-lang.c:907:23: warning: this statement may fall 
through [-Wimplicit-fallthrough=]
  TREE_ADDRESSABLE (x) = 1;
../../gcc-8.0.0/gcc/gm2/gm2-lang.c:909:7: note: here
       default:
       ^~~~~~~
../../gcc-8.0.0/gcc/gm2/Make-lang.in:712: recipe for target 'gm2/gm2-lang.o' 
failed
make[3]: *** [gm2/gm2-lang.o] Error 1
make[3]: Leaving directory '/home/christoph/gm2build/gcc'
cp: cannot stat 'stage1/gm2/cc1gm2': No such file or directory
../../gcc-8.0.0/gcc/gm2/Make-lang.in:588: recipe for target 'cc1gm2' failed
make[2]: *** [cc1gm2] Error 1
make[2]: Leaving directory '/home/christoph/gm2build/gcc'
Makefile:4302: recipe for target 'all-gcc' failed
make[1]: *** [all-gcc] Error 2
make[1]: Leaving directory '/home/christoph/gm2build'
Makefile:917: recipe for target 'all' failed
make: *** [all] Error 2

Regards
Christoph