Dear Marc,

On OpenBSD-current (and I suppose any other OBSD version) there's a PITA bug in latest Gambit when compiled with --enable-cplusplus. I tried it with G++ 4.7.2 and 4.6.3. Possibly this bug exists also with any Gambit version.

The bug is extremely easily reproducible:

$ gsc Gambit v4.6.6

,q

terminate called after throwing an instance of '___throw_struct' terminate called recursively Abort trap (core dumped) $

I've been hunting this bug down quite extensively now and it appears to me that Gambit's normal way of terminating (at least on OBSD and Debian) is by throwing an uncaught exception, containing a ___throw_struct whose content is a __SCMOBJ containing a fixnum by the number one (1)???

But if so, why is not an uncaught exception error printed at gsctermination on every platform (which is g++'s default behavior)???

Would greatly appreciate a hand in resolving this bug, it takes time generating the core file, clutters the terminal by requiring you to run reset after every gsc session, and primarily, it gives a terrible 'out of control' sense to the console interaction!..

Find my notes in hunting this one down below. If I can check for or try anything particular as to resolve the originating cause, please just tell me what.

Thanks! Mikael

--

I've tried to track this down while comparing execution flows between OpenBSD and Debian and I'm a but puzzled:

Fundamentally the error is caused by the ___THROW (err); inside ___propagate_error defined in lib/setup.c, row ~1895 , see GDB session below for this.

The invocation to ___propagate_error is made from one place in all Gambit namely |##exit-with-err-code-no-cleanup| in lib/_kernel.scm:~4356.

On both OBSD and Debian, ___USE_SETJMP is *not defined* so it's the *second* set of exception handling macros including ___THROW in include/gambit.h that are used i.e.:

#define ___BEGIN_TRY { ___err = ___FIX(___NO_ERR); try { #define ___END_TRY } catch (___throw_struct ts) { ___err = ts.err; } } #define ___THROW(e)do { ___throw_struct ts; ts.err = e; throw (ts); } while (0) #define ___ON_THROW(stat1,stat2) \ ___ON_THROW_AUX(,stat1,stat2)

So this is the throw() that causes the uncaught exception, that produces this entire error.

On both OBSD and Debian, on normal Gambit termination, |##exit-with-err-code-no-cleanup| is invoked with the fixnum 1 as argument, leading to a ___THROW with 4 as argument, 4 is Gambit's internal object representation for the fixnum 1.

I tried to trace the source of the invocation to |##exit-with-err-code-no-cleanup| but didn't quite succeed.

I tried in three ways of catching this thrown exception, and they failed (listing of methods and code used below).

Below are the outputs from a related GDB session and failed attempts to hunt down

The console output doesn't show anything, and except for a section highlighted below, configure doesn't seem to show anything.

*GDB output: Tracking down the location of the throw() for the uncaught exception* # egdb gsc GNU gdb (GDB) 7.5 Copyright (C) 2012 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html

This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-unknown-openbsd5.2". For bug reporting instructions, please see: http://www.gnu.org/software/gdb/bugs/... Reading symbols from /usr/bin/gsc...done. (gdb) run Starting program: /usr/bin/gsc Gambit v4.6.6

Program received signal SIGTSTP, Stopped (user). 0x000016f1c39a951a in select () at <stdin>:2 2 <stdin>: No such file or directory. (gdb) catch catch Catchpoint 1 (catch) (gdb) catch throw Catchpoint 2 (throw) (gdb) catch exception Unable to insert catchpoint. Is this an Ada main program? (gdb) catch unknown exception Undefined catch command: "unknown exception". Try "help catch". (gdb) catch exception unhandled Unable to insert catchpoint. Is this an Ada main program? (gdb) cont Continuing. ,q Catchpoint 2 (exception thrown), __cxxabiv1::__cxa_throw (obj=0x16f1c758c480, tinfo=0x16efbce1e490 <typeinfo for ___throw_struct>, dest=0x0) at /usr/obj/gcc-4.7.2/gcc-4.7.2/libstdc++-v3/libsupc++/eh_throw.cc:70 70 /usr/obj/gcc-4.7.2/gcc-4.7.2/libstdc++-v3/libsupc++/eh_throw.cc: No such file or directory. (gdb) bt #0 __cxxabiv1::__cxa_throw (obj=0x16f1c758c480, tinfo=0x16efbce1e490 <typeinfo for ___throw_struct>, dest=0x0) at /usr/obj/gcc-4.7.2/gcc-4.7.2/libstdc++-v3/libsupc++/eh_throw.cc:70 #1 0x000016efbc830f78 in ___propagate_error(long) () #2 0x000016efbc855a7b in ___H__20___kernel(___processor_state_struct*) () #3 0x000016efbc831026 in ___call(int, long, long) () #4 0x000016efbc832cee in ___setup(___setup_params_struct*) () #5 0x000016efbc847a0e in ___main(___mod_or_lnk_union* (*)(___global_state_struct*)) () #6 0x000016efbc83c3b3 in ___main_char(int, char**, ___mod_or_lnk_union* (*)(___global_state_struct*), char*) () #7 0x000016efbc830216 in main (argc=1, argv=0x7f7ffffbdfa0) at _gsc_.c:13627 (gdb)

*Failed attempts to catch the exception* (A) Hooking the uncaught exception handler via std::set_terminate(); , see example code for this below. Funny enough this did not work, it gave "no active exception".

(B) Tried running a REPL inside a try { .. } catch statement and do ,q from it. Did not work.

(C) Tried to put debug output include/gambit.h and lib/os_base.c around 1) Gambit's main() procedure and 2) around the try { .. } catch-code that actually is there. I would guess the code modified in 2) not runs though as it only runs when longjumps are not on. Printed "Gambit Started.\Past ___setup_base_module()\nInto ___main.\n". and that's all, all the way until C++' uncaught exception handler prints its error message. So, did not work.

* * (A) code* ; http://efesx.com/2010/03/21/catching-uncaught-exceptions-within-terminate/

(c-declare #<<c-declare

#include <iostream> #include <stdexcept> #include <exception>

void our_terminate (void) { printf("Terminating..\n");

static bool tried_throw = false;

try { if (!tried_throw++) throw; std::cout << "no active exception" << std::endl; } catch (___SCMOBJ err) { printf("Got SCMOBJ %lld.\n",err); } catch (const std::runtime_error &err) { std::cout << "caught a runtime_error. what(): " << err.what() << std::endl; } catch (...) { std::cout << "unknown exception occurred." << std::endl; }

}

c-declare )

(c-initialize #<<c-initialize

std::set_terminate(our_terminate);

c-initialize )

* * (B) code* (c-define (runscm thunk) (scheme-object) void "runscm" "" (print "(runscm): Running thunk.\n") (thunk) (print "(runscm): Back from thunk.\n"))

(define (c++-try-catch thunk) ((c-lambda (scheme-object) void #<<c-lambda-end

___SCMOBJ thunk = ___arg1; try { runscm(thunk); } catch (___throw_struct e) { fprintf(stderr,"Caught a ___throw_struct!\n"); } catch (...) { fprintf(stderr,"Caught some other excepion.\n"); }

c-lambda-end ) thunk))

(c++-try-catch ##repl)

* * (C) code*

include/gambit.h

#ifdef ___USE_SETJMP ... #define ___BEGIN_TRY { ___err = ___FIX(___NO_ERR); try { #define ___END_TRY } catch (___throw_struct ts) { printf("___END_TRY caught a ___throw_struct.\n"); ___err = ts.err; } } #define ___THROW(e)do { ___throw_struct ts; ts.err = e; printf(stderr,"___THROW throws a ___throw_struct.\n"); throw (ts); } while (0) #define ___ON_THROW(stat1,stat2) \ ___ON_THROW_AUX(,stat1,stat2)

#endif

#define ___ON_THROW_AUX(decl,stat1,stat2) \ do { \ fprintf(stderr,"___ON_THROW_AUX\n"); \ ___SCMOBJ ___err; decl \ ___BEGIN_TRY stat1; ___END_TRY \ if (___err != ___FIX(___NO_ERR)) stat2; \ } while (0)

lib/os_base.c: ___EXP_FUNC(int,___main_char) ___P((int argc, char *argv[], ___mod_or_lnk (*linker)(___global_state_struct*), char *script_line), (argc, argv, linker, script_line) int argc; char *argv[]; ___mod_or_lnk (*linker)(); char *script_line;) { int result; fprintf(stderr,"Gambit started.\n");

try {

if (___setup_base_module () != ___FIX(___NO_ERR)) result = ___EXIT_CODE_OSERR; else { fprintf(stderr,"Past ___setup_base_module()\n"); if (___NONNULLCHARSTRINGLIST_to_NONNULLUCS_2STRINGLIST (argv, &___program_startup_info.argv) != ___FIX(___NO_ERR)) result = ___EXIT_CODE_SOFTWARE; else { if (___CHARSTRING_to_UCS_2STRING (script_line, &___program_startup_info.script_line) != ___FIX(___NO_ERR)) result = ___EXIT_CODE_SOFTWARE; else { fprintf(stderr,"Into ___main\n"); result = ___main (linker); fprintf(stderr,"Out of ___main\n");

___free_UCS_2STRING (___program_startup_info.script_line); }

___free_NONNULLUCS_2STRINGLIST (___program_startup_info.argv); }

fprintf(stderr,"Into ___cleanup_base_module\n"); ___cleanup_base_module (); fprintf(stderr,"Out of ___cleanup_base_module.\n"); } } catch (___throw_struct e) { fprintf(stderr,"Caught a ___throw_struct!\n"); } catch (...) { fprintf(stderr,"Caught some other excepion.\n"); }

fprintf(stderr,"Gambit ended.\n");

return result; }

*./configure log* $ CXFLAGS="-g -ggdb -gdwarf-3 -gstrict-dwarf -O0" ./configure --enable-cplusplus --enable-single-host (note misspelling on env var, anyhow) checking build system type... amd64-unknown-openbsd5.2 checking host system type... amd64-unknown-openbsd5.2 checking target system type... amd64-unknown-openbsd5.2 checking for gcc... gcc checking for C compiler default output file name... a.out checking whether the C compiler works... yes checking whether we are cross compiling... no checking for suffix of executables... checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking how to run the C preprocessor... gcc -E checking for g++... g++ checking whether we are using the GNU C++ compiler... yes checking whether g++ accepts -g... yes checking how to run the C++ preprocessor... g++ -E checking for grep that handles long lines and -e... /usr/bin/grep checking for egrep... /usr/bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking for void*... yes checking size of void*... 8 checking for long... yes checking size of long... 8 checking for bool... yes checking whether g++ defines __GNUC__... yes checking whether g++ defines __clang__... checking whether g++ defines __llvm__... checking whether g++ defines _MSC_VER... checking errno.h usability... yes checking errno.h presence... yes checking for errno.h... yes checking float.h usability... yes checking float.h presence... yes checking for float.h... yes checking signal.h usability... yes checking signal.h presence... yes checking for signal.h... yes checking stdio.h usability... yes checking stdio.h presence... yes checking for stdio.h... yes checking for stdlib.h... 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(cached) yes checking sys/sysctl.h usability... no checking sys/sysctl.h presence... yes configure: WARNING: sys/sysctl.h: present but cannot be compiled - This is documented at http://fxr.watson.org/fxr/source/sys/sysctl.h?v=OPENBSD , doesn't look like anything that would crash an ordinary Gambit session?? configure: WARNING: sys/sysctl.h: check for missing prerequisite headers? configure: WARNING: sys/sysctl.h: see the Autoconf documentation configure: WARNING: sys/sysctl.h: section "Present But Cannot Be Compiled" configure: WARNING: sys/sysctl.h: proceeding with the preprocessor's result configure: WARNING: sys/sysctl.h: in the future, the compiler will take precedence configure: WARNING: ## -------------------------------------- ## configure: WARNING: ## Report this to gambit@iro.umontreal.ca ## configure: WARNING: ## -------------------------------------- ## checking for sys/sysctl.h... yes checking crt_externs.h usability... no checking crt_externs.h presence... no checking for crt_externs.h... no checking ws2tcpip.h usability... no checking ws2tcpip.h presence... no checking for ws2tcpip.h... no checking TargetConditionals.h usability... no checking TargetConditionals.h presence... no checking for TargetConditionals.h... no checking for socklen_t... yes checking for library containing asin... none required checking for library containing dlopen... none required checking for library containing shl_load... no checking for library containing socket... none required checking for library containing gethostbyname... none required checking for library containing hstrerror... none required checking for library containing openpty... -lutil checking for library containing WSAStartup... no checking for pipe... yes checking for socketpair... yes checking for chdir... yes checking for execvp... yes checking for getgrnam... yes checking for getpid... yes checking for getppid... yes checking for getpwnam... yes checking for ioctl... yes checking for link... yes checking 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