GCC 7.1.1 RISCV compilation (link) failures, incompatible ABI - gcc

Question

I'm having difficulty doing basic compilation & link for RISCV on the latest GCC for RISCV on a windows 7-64bit platform.
Tools installed: 7.1.1-2-20170912-2255 gotten from https://github.com/gnu-mcu-eclipse/riscv-none-gcc/releases/
Platform: Windows 7, 64 bit, no cygwin
Program:
#include <stdint.h>
int32_t iBlahblah;
int main (void)
{
while(1)
iBlahblah++;
return 0;
}
Command line:
"c:\Program Files\GNU MCU Eclipse\RISC-V Embedded GCC\7.1.1-2-20170912-2255\bin\riscv64-unknown-elf-gcc.exe" -c hello.c -o hello -march=rv32imac -mabi=ilp32 -Os
"c:\Program Files\GNU MCU Eclipse\RISC-V Embedded GCC\7.1.1-2-20170912-2255\bin\riscv64-unknown-elf-gcc.exe" -o hello.elf -march=rv32imac -mabi=ilp32 -Os -Wl,-Map=hello.lst hello.o
Output:
c:/program files/gnu mcu eclipse/risc-v embedded gcc/7.1.1-2-20170912-2255/bin/../lib/gcc/riscv64-unknown-elf/7.1.1/../../../../riscv64-unknown-elf/bin/ld.exe: hello.o: ABI is incompatible with that of the selected emulation: target emulation `elf64-littleriscv' does not match `elf32-littleriscv'
c:/program files/gnu mcu eclipse/risc-v embedded gcc/7.1.1-2-20170912-2255/bin/../lib/gcc/riscv64-unknown-elf/7.1.1/../../../../riscv64-unknown-elf/bin/ld.exe: failed to merge target specific data of file hello.o
c:/program files/gnu mcu eclipse/risc-v embedded gcc/7.1.1-2-20170912-2255/bin/../lib/gcc/riscv64-unknown-elf/7.1.1/../../../../riscv64-unknown-elf/lib/rv32imac/ilp32\libg.a(lib_a-exit.o): In function `.L0 ': exit.c:(.text.exit+0x1e): undefined reference to `_exit'
c:/program files/gnu mcu eclipse/risc-v embedded gcc/7.1.1-2-20170912-2255/bin/../lib/gcc/riscv64-unknown-elf/7.1.1/../../../../riscv64-unknown-elf/bin/ld.exe: hello.elf(.text): relocation "iBlahblah+0x0 (type R_RISCV_HI20)" goes out of range
c:/program files/gnu mcu eclipse/risc-v embedded gcc/7.1.1-2-20170912-2255/bin/../lib/gcc/riscv64-unknown-elf/7.1.1/../../../../riscv64-unknown-elf/bin/ld.exe: hello.o: file class ELFCLASS64 incompatible with ELFCLASS32
c:/program files/gnu mcu eclipse/risc-v embedded gcc/7.1.1-2-20170912-2255/bin/../lib/gcc/riscv64-unknown-elf/7.1.1/../../../../riscv64-unknown-elf/bin/ld.exe: final link failed: File in wrong format
collect2.exe: error: ld returned 1 exit status
The big question is how do I resolve the "ABI is incompatible with that of the selected emulation"? We can ignore the other issues regarding relocation, exit, etc. because my larger build environment takes care of that (it builds for many platforms, just not RISCV at the moment).

Answer 1

riscv64-unknown-elf-gcc.exe -c hello.c -o hello -march=rv32imac -mabi=ilp32 -Os
This part is wrong. Your gcc tolchain docs says https://gnu-mcu-eclipse.github.io/toolchain/riscv/
riscv64-unknown-elf-gcc vs riscv32-unknown-elf-gcc
With lots of architectures and systems supported, GCC recommends prefixing the binaries with a unique tuple:
<arch>-<vendor>-<os>-<libc/abi>-
The current RISC-V prefixes for the bare metal toolchains are riscv64-unknown-elf- and riscv32-unknown-elf-.
Well, don’t be confused by this unfortunate names. The 64 or 32 attached to the architecture ... It does not mean either that the compiler produces 64-bits or 32-bits RISC-V binaries. Actually, the compilers produce both 32/64-bits binaries, based on -march and -mabi. The only difference are defaults, when the compiler are invoked without the -march and -mabi explicitly set on the command line.
Try to use riscv32-unknown-elf-gcc.exe for compiling programs for 32-bit riscv platform (with arch & abi having r32 & 32 parts in their names), it should use correct 32-bit CRT files.
There is some support for multilib, when riscv64 will search for 32-bit libs (https://gnu-mcu-eclipse.github.io/toolchain/riscv/#multiple-libraries, https://gnu-mcu-eclipse.github.io/blog/2017/09/13/riscv-none-gcc-v7-1-1-2-20170912-released/, https://gcc.gnu.org/onlinedocs/gccint/Target-Fragment.html MULTILIB_OPTIONS), but something was wrong. Please, post gcc -v .... -o your_program.bin results for riscv32 compiler, riscv64 compiler and several march/mabi combinations.