32-bit buildbot builders broken [Re: Your commit 'Build GDB as a C++ program by default' broke GDB]

[Pedro Alves <palves@redhat.com>]

On 04/21/2016 12:04 AM, sergiodj+buildbot@sergiodj.net wrote:
> Hello there,
> 
> Your commit:
> 
> 	Build GDB as a C++ program by default
> 	a23585089d7ba710b238d3d1ab3d34320afa48d0
> 
> broke GDB.  Please fix it, or the GDB gods will get you.
> 


> Full Build URL:
> 	<http://gdb-build.sergiodj.net/builders/Fedora-i686/builds/3465>
> 

This is "Fedora-i686", a 32-bit builder.

> 
> g++ -g -O2   -I. -I../../binutils-gdb/gdb -I../../binutils-gdb/gdb/common
> -I../../binutils-gdb/gdb/config
...
> -I../../binutils-gdb/gdb/../libdecnumber  -I../../binutils-gdb/gdb/gnulib/import -Ibuild-gnulib/import   -DTUI=1  -I/usr/include/python2.7 -I/usr/include/python2.7 -Wall -Wpointer-arith -Wno-unused -Wunused-value -Wunused-function -Wno-switch -Wno-char-subscripts -Wempty-body -Wno-sign-compare -Wno-write-strings -Wno-narrowing -Wformat-nonliteral -Werror -c -o linux-thread-db.o -MT linux-thread-db.o -MMD -MP -MF .deps/linux-thread-db.Tpo ../../binutils-gdb/gdb/linux-thread-db.c
> In file included from ../../binutils-gdb/gdb/i386-linux-nat.c:25:0:
> ../../binutils-gdb/gdb/i386-linux-nat.c: In function void fetch_regs(regcache*, int):
> ../../binutils-gdb/gdb/i386-linux-nat.c:207:46: error: cast from elf_greg_t (*)[27] {aka long long unsigned int (*)[27]} to int loses precision [-fpermissive]
>    if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)


... however this error is exactly what you get if you compile with a
64-bit compiler, and forget to pass -m32 to gcc/g++.  IOW, 
it compiles i386-linux-nat.c as if for a 64-bit host, which fails.

So I suspect the builder is using CC="gcc -m32", and now that a C++ compiler
is involved, it needs to be updated to pass CXX="g++ -m32" as well.

Thanks,
Pedro Alves