Re: [musl] Musl compiled gawk coredumps. How to find out where?

[Rich Felker <dalias@libc.org>]

On Fri, Sep 24, 2021 at 02:53:39PM +0000, Ivo Palli wrote:
> Ok, I've got some valgrind output:
> 
> Program terminated with signal SIGABRT, Aborted.
> #0  __restore_sigs (set=set@entry=0x1ffeffe910) at ./arch/x86_64/syscall_arch.h:40
> 40              return ret;
> (gdb) backtrace
> #0  __restore_sigs (set=set@entry=0x1ffeffe910) at ./arch/x86_64/syscall_arch.h:40
> #1  0x00000000004cf1c4 in raise (sig=sig@entry=6) at src/signal/raise.c:11
> #2  0x00000000004c96ea in abort () at src/exit/abort.c:11
> #3  0x0000000000452f16 in catchsig (sig=<optimized out>) at main.c:1231
> #4  catchsig (sig=<optimized out>) at main.c:1217
> #5  <signal handler called>
> #6  get_meta (p=p@entry=0x4a5af50 "\260\232\243\001") at src/malloc/mallocng/meta.h:141
> #7  0x00000000004ca62c in __libc_free (p=0x4a5af50) at src/malloc/mallocng/free.c:105
> #8  0x0000000000459d57 in r_unref (tmp=tmp@entry=0x48728c8) at node.c:492
> #9  0x00000000004456e5 in unref (r=0x48728c8) at awk.h:1898
> #10 purge_record () at field.c:360
> #11 0x0000000000445f36 in set_record (
>     buf=0x549bdae "SIZE\t1KB\t192758\t112698119\nSIZE\t4KB\t462090\t1122421206\nSIZE\t16KB\t355596\t3138948391\nSIZE\t64KB\t413028\t13558910172\nSIZE\t256KB\t1014012\t165385758947\nSIZE\t1MB\t2546508\t1346405498466\nSIZE\t10MB\t480844\t1602796961"..., cnt=25, fw=0x0) at field.c:269
> #12 0x000000000044e765 in inrec (iop=<optimized out>, errcode=errcode@entry=0x1ffefffa50) at io.c:608
> #13 0x00000000004414f8 in h_interpret (code=<optimized out>) at interpret..h:1289
> #14 0x0000000000402631 in main (argc=<optimized out>, argv=<optimized out>) at main.c:516
> (gdb) frame 8
> #8  0x0000000000459d57 in r_unref (tmp=tmp@entry=0x48728c8) at node.c:492
> 492             mpfr_unset(tmp);
> (gdb) print tmp
> $1 = (NODE *) 0x48728c8
> (gdb) print *tmp
> $2 = {sub = {nodep = {l = {lptr = 0x100000002, li = 0x100000002, ll = 4294967298, lp = 0x100000002}, r = {rptr = 0x4a5af50, preg = {0x4a5af50, 0x0}, av = 0x4a5af50, bv = 0x4a5af50,
>         uptr = 0x4a5af50, iptr = 0x4a5af50}, x = {extra = 0x0, aptr = 0x0, xl = 0}, name = 0x4e <error: Cannot access memory at address 0x4e>, reserved = 75884000, rn = 0x8, cnt = 0,
>       reflags = 4294967295}, val = {nm = {fltnum = 2.1219957919534036e-314, mpnum = {{_mpfr_prec = 4294967298, _mpfr_sign = 77967184, _mpfr_exp = 0, _mpfr_d = 0x0}}, mpi = {{
>             _mp_alloc = 2, _mp_size = 1, _mp_d = 0x4a5af50}}}, rndmode = 78, sp = 0x485e5e0 "27499184", slen = 8, sref = 0, idx = -1, wsp = 0x0, wslen = 0, typre = 0x0}},
>   type = Node_val, flags = 2108}
> 
> 
> ==43165== Conditional jump or move depends on uninitialised value(s)
> ==43165==    at 0x4CA82E: enframe (meta.h:204)
> ==43165==    by 0x462EAB: xrealloc (xalloc.h:173)
> ==43165==    by 0x462EAB: xpalloc (dfa.c:850)
> ==43165==    by 0x462F52: copy.isra.10 (dfa.c:2043)
> ==43165==    by 0x464BC1: dfaanalyze (dfa.c:2490)
> ==43165==    by 0x4679F2: dfacomp (dfa.c:3527)
> ==43165==    by 0x45F596: make_regexp (re.c:230)
> ==43165==    by 0x413740: make_regnode (awkgram.y:5026)
> ==43165==    by 0x416C08: yyparse (awkgram.y:505)
> ==43165==    by 0x41B443: parse_program (awkgram.y:2587)
> ==43165==    by 0x4025AB: main (main.c:469)
> ==43165==  Uninitialised value was created by a stack allocation
> ==43165==    at 0x4760E3: re_compile_internal (regcomp.c:755)
> ==43165==
> ==43165== Conditional jump or move depends on uninitialised value(s)
> ==43165==    at 0x4CA82E: enframe (meta.h:204)
> ==43165==    by 0x4D837D: __libc_realloc (realloc.c:46)
> ==43165==    by 0x46B977: test_realloc (regex_internal.h:476)
> ==43165==    by 0x46B977: re_dfa_add_node (regex_internal.c:1438)
> ==43165==    by 0x46BA7A: duplicate_node (regcomp.c:1643)
> ==43165==    by 0x46BC59: duplicate_node_closure (regcomp.c:1566)
> ==43165==    by 0x46E3CF: calc_eclosure_iter.isra.30 (regcomp.c:1745)
> ==43165==    by 0x47660C: calc_eclosure (regcomp.c:1708)
> ==43165==    by 0x47660C: analyze (regcomp.c:1235)
> ==43165==    by 0x47660C: re_compile_internal (regcomp.c:821)
> ==43165==    by 0x476EB9: re_compile_pattern (regcomp.c:256)
> ==43165==    by 0x45F0FA: make_regexp (re.c:215)
> ==43165==    by 0x413765: make_regnode (awkgram.y:5031)
> ==43165==    by 0x416C08: yyparse (awkgram.y:505)
> ==43165==    by 0x41B443: parse_program (awkgram.y:2587)
> ==43165==  Uninitialised value was created by a stack allocation
> ==43165==    at 0x4760E3: re_compile_internal (regcomp.c:755)
> ==43165==
> ==43165== Conditional jump or move depends on uninitialised value(s)
> ==43165==    at 0x4CA82E: enframe (meta.h:204)
> ==43165==    by 0x462D44: xmalloc (xalloc.h:147)
> ==43165==    by 0x46770C: xnmalloc (xalloc.h:134)
> ==43165==    by 0x46770C: dfassbuild (dfa.c:3455)
> ==43165==    by 0x46770C: dfacomp (dfa.c:3522)
> ==43165==    by 0x45F596: make_regexp (re.c:230)
> ==43165==    by 0x413765: make_regnode (awkgram.y:5031)
> ==43165==    by 0x416C08: yyparse (awkgram.y:505)
> ==43165==    by 0x41B443: parse_program (awkgram.y:2587)
> ==43165==    by 0x4025AB: main (main.c:469)
> ==43165==  Uninitialised value was created by a stack allocation
> ==43165==    at 0x4760E3: re_compile_internal (regcomp.c:755)
> ==43165==
> 
> Since it looks like a gawk bug, not directly anything to do with
> musl, I'll see if I can submit a bug report with the gawk
> maintainers.

Here valgrind is not succeeding in interposing its own malloc
debugging, so you're not getting meaningful output. If you don't have
an environment for running musl-linked programs under valgrind (easy
if you have a musl-based distro, but if not it probably needs some
patches for whatever valgrind is getting wrong), see what happens if
you build the same version of gawk against glibc and run it under
valgrind. I would expect the same error to be visible.

Rich