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| ID | Project | Category | View Status | Date Submitted | Last Update | ||||||
| 0004538 | OCaml | OCaml general | public | 2008-04-23 12:26 | 2012-09-06 19:17 | ||||||
| Reporter | jsk | ||||||||||
| Assigned To | |||||||||||
| Priority | normal | Severity | crash | Reproducibility | always | ||||||
| Status | acknowledged | Resolution | open | ||||||||
| Platform | OS | OS Version | |||||||||
| Product Version | 3.10.2 | ||||||||||
| Target Version | later | Fixed in Version | |||||||||
| Summary | 0004538: Remotely debugging multi-threaded bytecode program causes segmentation fault. | ||||||||||
| Description | === Operating System === Type: Ubuntu Linux Version: 7.10 Platform: x86 === OCaml Installation === Version: 3.10.2 Build: x86 === Summary of Fault === When the attached program is compiled as a bytecode executable, remotely debugging the program causes it to terminate with a segmentation fault, when stepping through manually on the debugger. === Reproduction Steps === 1. Compile the attached program with ocamlc: ocamlc -custom -thread -g unix.cma threads.cma test.ml -o test.exe 2. Start ocamldebug in remote debugging mode (manual loading): ocamldebug -s <socket-name> test.exe set loadingmode manual goto 0 3. Manually start the program (possibly on another machine): CAML_DEBUG_SOCKET=<socket_name> ./test.exe 4. Repeatedly issue the following command to ocamldebug: step === Fault Description === After some number of steps (different number each time), the executable (test.exe) terminates with a "Segmentation Fault (core dumped)" message (See the attached core dump files). Analysis of the core dumps with gdb invariably points to the following location: Program terminated with signal 11, Segmentation fault. #0 0x08073570 in caml_interprete (prog=0x80ad1e8, prog_size=48680) at interp.c:284 284 curr_instr = *pc++; (gdb) backtrace #0 0x08073570 in caml_interprete (prog=0x80ad1e8, prog_size=48680) at interp.c:284 #1 0x0805bd3f in caml_main (argv=0xbf83daa4) at startup.c:414 #2 0x0805befb in main (argc=1, argv=0xbf83daa4) at main.c:56 | ||||||||||
| Tags | No tags attached. | ||||||||||
| Attached Files |  test.ml [^] (1,222 bytes) 2008-04-23 12:26 cores.zip [^] (344,748 bytes) 2008-04-23 12:41 | ||||||||||
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(0004498) jsk (reporter) 2008-04-23 12:54 edited on: 2008-04-25 10:10 |
Some further info: By modifying the lines between "Mutex.lock" and "Mutex.unlock", it's possible to coerce ocamlrun into producing various errors (other than segmentation faults). For example, replace the pair of print_string statements with the following statement: Printf.printf "Thread %n Iteration %n" (Thread.id (Thread.self ())) i; On my system, if this change is made, then the segmentation fault goes away, but only to be replaced with the following error: Fatal error: bad opcode (65726854) Cheers Jonathan --- Jonathan Knowles Citrix Systems Research & Development |
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(0004567) doligez (manager) 2008-08-04 16:55 |
reproduced with 3.11+dev14 on Mac OS X 10.5.4 |
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(0005352) doligez (manager) 2010-04-20 14:38 |
the bug is still here in 3.11.2 and 3.12.0+dev17 [Mac OS 10.6.3] |
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(0007645) doligez (manager) 2012-07-06 16:10 |
Note that the debugger uses the fork() system call to do checkpointing of the process. The interactions between fork() and threads are tricky and platform-dependent, so it's not really a surprise that the debugger would fail on a multi-threaded program. Worse, it's not clear that we can do anything about it. |
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Issue History |
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| Date Modified | Username | Field | Change |
| 2008-04-23 12:26 | jsk | New Issue | |
| 2008-04-23 12:26 | jsk | File Added: test.ml | |
| 2008-04-23 12:34 | jsk | Note Added: 0004497 | |
| 2008-04-23 12:41 | jsk | File Added: cores.zip | |
| 2008-04-23 12:42 | jsk | Note Edited: 0004497 | |
| 2008-04-23 12:43 | jsk | Note Deleted: 0004497 | |
| 2008-04-23 12:54 | jsk | Note Added: 0004498 | |
| 2008-04-25 10:09 | jsk | Note Edited: 0004498 | |
| 2008-04-25 10:10 | jsk | Note Edited: 0004498 | |
| 2008-08-04 16:55 | doligez | Note Added: 0004567 | |
| 2008-08-04 16:55 | doligez | Status | new => acknowledged |
| 2010-04-20 14:38 | doligez | Note Added: 0005352 | |
| 2012-07-06 16:10 | doligez | Note Added: 0007645 | |
| 2012-07-06 16:10 | doligez | Target Version | => 4.01.0+dev |
| 2012-07-31 13:36 | doligez | Target Version | 4.01.0+dev => 4.00.1+dev |
| 2012-09-06 19:17 | frisch | Target Version | 4.00.1+dev => later |
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Issue History |
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