Porting MicroPython to SwissMicros DM42 / DMCP

C programming, build, interpreter/VM.
Target audience: MicroPython Developers.
Posts: 15
Joined: Sun Apr 12, 2020 10:12 pm

Re: Porting MicroPython to SwissMicros DM42 / DMCP

Post by fnord » Fri May 22, 2020 7:03 pm

I tried to reproduce this in the embedding example, and it indeed happens there, too.

Adding the following to hello-embed.c:

Code: Select all

    // heap exhaustion test
    const char str_heaptest[] =
        "import gc\n"
        "for i in range(1000):\n"
        "  print(\"mem: %d / %d\"%(gc.mem_alloc(), gc.mem_free()))";
    if (execute_from_str(str_heaptest)) {
results in:

Code: Select all

mem: 15808 / 448
mem: 15904 / 352
mem: 16000 / 256
mem: 16096 / 160
Segmentation fault (core dumped)
And this is what gdb has to say about it:

Code: Select all

Program received signal SIGSEGV, Segmentation fault.
gc_collect_root (ptrs=ptrs@entry=0x7fffffffd410, len=2305825417027650942) at ../../py/gc.c:345
345             void *ptr = ptrs[i];
(gdb) backtrace
#0  gc_collect_root (ptrs=ptrs@entry=0x7fffffffd410, len=2305825417027650942) at ../../py/gc.c:345
#1  0x00000000004142f8 in gc_helper_collect_regs_and_stack () at ../../lib/utils/gchelper_generic.c:154
#2  0x0000000000414297 in gc_collect () at libmicropython.c:44
#3  0x0000000000401db5 in gc_alloc (n_bytes=n_bytes@entry=32, alloc_flags=alloc_flags@entry=0) at ../../py/gc.c:490
#4  0x0000000000414376 in m_malloc (num_bytes=num_bytes@entry=32) at ../../py/malloc.c:86
#5  0x000000000040ddc7 in mp_obj_new_str_from_vstr (type=0x419800 <mp_type_str>, vstr=0x7fffffffd550) at ../../py/objstr.c:2069
#6  0x000000000040efb7 in mp_obj_str_binary_op (op=<optimized out>, lhs_in=<optimized out>, rhs_in=<optimized out>) at ../../py/objstr.c:342
#7  0x000000000040a3eb in mp_binary_op (op=MP_BINARY_OP_MODULO, lhs=0x4266a0 <heap+1504>, rhs=0x42a080 <heap+16320>) at ../../py/runtime.c:570
#8  0x0000000000412aac in mp_execute_bytecode (code_state=code_state@entry=0x7fffffffd6f0, inject_exc=inject_exc@entry=0x0) at ../../py/vm.c:1346
#9  0x000000000040c06b in fun_bc_call (self_in=0x4262c0 <heap+512>, n_args=0, n_kw=<optimized out>, args=<optimized out>) at ../../py/objfun.c:283
#10 0x0000000000401290 in execute_from_str (str=0x7fffffffd850 "import gc\nfor i in range(1000):\n  print(\"mem: %d / %d\"%(gc.mem_alloc(), gc.mem_free()))") at hello-embed.c:49
#11 0x0000000000401513 in main () at hello-embed.c:111
(gdb) print i
$3 = 894

Posts: 15
Joined: Sun Apr 12, 2020 10:12 pm

Re: Porting MicroPython to SwissMicros DM42 / DMCP

Post by fnord » Mon Sep 28, 2020 8:36 pm

jimmo wrote:
Thu May 07, 2020 3:17 am
fnord wrote:
Wed May 06, 2020 8:37 pm
Whereas the following code causes the program to crash:
It sounds like the GC is crashing. I initially wondered if it was filling up the entire heap with QSTR pools, but I don't think that exact code will result in any QSTRs being created (only strings which can be GC'ed).

Any chance you can post what you've got so far to github so I can take a look?
Hi Jimmo, could I ask you to have a look at this again?
I'm kind of stuck, because I don't know how to fix the GC problem...

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