Original bug ID: 7366
Reporter: pmetras
Status: resolved (set by @xavierleroy on 2017-02-16T08:53:43Z)
Resolution: not a bug
Priority: normal
Severity: minor
Platform: i386
OS: Minix3
OS Version: 3.4.0
Category: otherlibs
Monitored by: @gasche

Bug description

The testsuite fails for some tests in lib-threads but I was unable to find the reason. This is related to the generated byte code. For instance, the test testsuite/tests/lib-threads/socketsbuf.ml fails, when executed with the just generated from sources OCaml version. But it passes if the same OCaml version is installed in /usr/local! The same bug occurs for testsuite/tests/lib-threads/fileio.ml.

$ ../byterun/ocamlrun -b -I ../stdlib -I ../otherlibs/threads -I ../otherlibs/unix ./program
Thread 2 killed on uncaught exception Sys_blocked_io
Raised by primitive operation at file "pervasives.ml", line 415, characters 4-749
Called from file "socketsbuf.ml", line 26, characters 10-23
Called from file "thread.ml", line 131, characters 8-14
Fatal error: exception Sys_blocked_io
Raised by primitive operation at file "pervasives.ml", line 415, characters 4-749
Called from file "socketsbuf.ml", line 26, characters 10-23
Called from file "socketsbuf.ml", line 46, characters 2-30

For people interested in system debugging, the exception occurs in byterun/unix.c, in function caml_read_fd.

The problem is in the generated code and the location of stdlib.

Steps to reproduce

To reproduce the bug it:

1. Compile the full OCaml distribution
2. Run the test socketsbuf.ml from the testsuite: it fails...
3. Compile it with "../byterun/ocamlrun ../ocamlc -g -I ../stdlib -w a -vmthread -I ../otherlibs/threads -I ../otherlibs/unix unix.cma threads.cma tests/lib-threads/socketsbuf.ml -o program". The testsuite version uses "-nostdlib -I ../testsuite/lib" parameters that does not affect the result and that we removed.
4. Run it with "../byterun/ocamlrun -b -I ../stdlib -I ../otherlibs/threads -I ../otherlibs/unix ./program". It fails again...
5. Become root and install the Ocaml distribution
6. Run again the program, but now you don't need all the includes as you use the system OCaml: "./program". It still fails...
7. Compile it with the system ocaml compiler: "ocamlc -g -w a -vmthread unix.cma threads.cma socketsbuf.ml -o program"
8. Run it: "./program". IT WORKS!
9. Delete the system OCaml installation in /usr/local.
10. Check you've done the job correctly: "./program" should print "./program: not found".
11. Run it again with "../byterun/ocamlrun -b -I ../stdlib -I ../otherlibs/threads -I ../otherlibs/unix ./program". IT STILL WORKS NOW!!!

You can see that the good and the bad programs have different sizes but I haven't seen an option to extract the generated bytecode and find the differences.

When the OCaml distribution is installed on the system, the shortest way to see the bug is:

1. Program generated by "ocamlc -g -w a -vmthread -I ../stdlib/ unix.cma threads.cma socketsbuf.ml -o program" fails
2. Program generated by "ocamlc -g -w a -vmthread unix.cma threads.cma socketsbuf.ml -o program" executes successfully

Additional information

Minix3 does not have system threads and I've adapted the testsuite to use VM threads instead.