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Re: Writing "absolutely" portable code

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On 01/11/2012 12:01 PM, ec429 wrote:
> On 11/01/12 16:52, James Kuyper wrote:
>> * A variable, whose value I want to check, has been optimized out of
>> existence.
> If that's happening with optimisation turned off, it's probably a bug, 
> which you should probably report.

I hadn't thought about that - I'll try to remember to do so the next
time it happens.

>> * I will advance though the program one step at a time. gdb will display
>> line 34, line 35, line 34, line 35, line 34, etc, which would be fine if
>> they were parts of loop, but is very disconcerting when one of those
>> lines is a comment and the other is a declaration. Eventually it stops
>> cycling between those line numbers, and jumps to line 39, and by
>> examination of the values of various variables, I conclude that what
>> it's actually been doing was executing the loop on lines 36 and 37.
> That sounds strongly like your source file is more recent than 
> executable.  gdb doesn't like it when the sources you have don't match 
> the binary you're debugging.
>> * I will single-step through a line of code that supposedly changes the
>> value of a variable, examining the value of that variable before and
>> after execution of the statement, and see the value unchanged. It
>> eventually gets changed, but during what is supposed to be the execution
>> of some other line of code much farther down in the code.
> Same as above, source/binary mismatch.

I agree, that is the most reasonable conclusion. That is why my first
step was to erase all object, library, and executable files created by
my build process, and rebuild from scratch. I continued to observe the
same behavior. This has happened in many different contexts.

I'm pretty good at writing platform-agnostic code; even my bugs are
usually platform-agnostic, so testing on our Irix machines generally was
just as good as testing on our Linux ones. Since we shut down our Irix
machines I've frequently had to fall back on debugging printf()s in
order to get sensible (i.e. corrected to make it appear as if no
optimizations were occurring) dumps of the program state.

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Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-09 02:26 -0800
  Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-09 11:47 +0000
    Re: Writing "absolutely" portable code Jens Gustedt <jens.gustedt@loria.fr> - 2012-01-09 13:56 +0100
    Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-09 05:45 -0800
      Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-09 14:46 +0000
        Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-10 01:11 -0800
    Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-09 15:58 +0000
    Re: Writing "absolutely" portable code falk@rahul.net (Edward A. Falk) - 2012-01-09 18:41 +0000
  Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-09 12:23 +0000
    Re: Writing "absolutely" portable code Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-09 08:45 -0500
      Re: Writing "absolutely" portable code superpollo <superpollo@tznvy.pbz> - 2012-01-09 15:02 +0100
        Re: Writing "absolutely" portable code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-09 16:11 +0000
    Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-09 05:56 -0800
      Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-09 15:07 +0000
        Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-10 01:21 -0800
          Re: Writing "absolutely" portable code Stephen Sprunk <stephen@sprunk.org> - 2012-01-10 13:20 -0600
            Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-11 06:57 -0800
          Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-11 09:23 +0000
  Re: Writing "absolutely" portable code jacob navia <jacob@spamsink.net> - 2012-01-09 13:48 +0100
    Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-09 13:11 +0000
      Re: Writing "absolutely" portable code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-09 05:27 -0800
        Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-09 13:41 +0000
          Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-09 06:09 -0800
      Re: Writing "absolutely" portable code jacob navia <jacob@spamsink.net> - 2012-01-09 14:35 +0100
        Re: Writing "absolutely" portable code Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-09 13:44 +0000
          Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-09 06:18 -0800
          Re: Writing "absolutely" portable code jacob navia <jacob@spamsink.net> - 2012-01-09 18:59 +0100
          Re: Writing "absolutely" portable code jacob navia <jacob@spamsink.net> - 2012-01-09 19:01 +0100
            Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-09 19:21 +0000
              Re: Writing "absolutely" portable code Richard <rgrdev_@gmail.com> - 2012-01-10 20:48 +0100
                Re: Writing "absolutely" portable code David Dyer-Bennet <dd-b@dd-b.net> - 2012-01-10 14:26 -0600
                Re: Writing "absolutely" portable code Richard <rgrdev_@gmail.com> - 2012-01-10 21:44 +0100
                Re: Writing "absolutely" portable code David Dyer-Bennet <dd-b@dd-b.net> - 2012-01-10 15:45 -0600
                Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-11 09:12 +0000
                Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-11 11:10 +0000
                Re: Writing "absolutely" portable code James Kuyper <jameskuyper@verizon.net> - 2012-01-11 11:52 -0500
                Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-11 17:01 +0000
                Re: Writing "absolutely" portable code James Kuyper <jameskuyper@verizon.net> - 2012-01-11 12:11 -0500
              Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-11 09:08 +0000
            Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-11 08:22 +0000
            Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-11 08:54 +0000
        Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-09 13:57 +0000
          Re: Writing "absolutely" portable code Seebs <usenet-nospam@seebs.net> - 2012-01-09 19:21 +0000
            Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-09 19:52 +0000
              Re: Writing "absolutely" portable code Seebs <usenet-nospam@seebs.net> - 2012-01-09 20:20 +0000
        Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-09 06:16 -0800
    Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-09 06:02 -0800
  Re: Writing "absolutely" portable code Keith Thompson <kst-u@mib.org> - 2012-01-09 14:50 -0800
    Re: Writing "absolutely" portable code Kaz Kylheku <kaz@kylheku.com> - 2012-01-09 23:20 +0000
      Re: Writing "absolutely" portable code Rui Maciel <rui.maciel@gmail.com> - 2012-01-10 00:23 +0000
    Re: Writing "absolutely" portable code Dirk Zabel <zabel@riccius-sohn.eu> - 2012-01-10 17:44 +0100
      Re: Writing "absolutely" portable code ArifulHossain tuhin <etothepowerpi@gmail.com> - 2012-01-11 07:13 -0800
      Re: Writing "absolutely" portable code Nick Bowler <nbowler@draconx.ca> - 2012-01-17 20:36 +0000
        Re: Writing "absolutely" portable code ec429 <ec429@cam.ac.uk> - 2012-01-17 23:06 +0000
          Re: Writing "absolutely" portable code blp@cs.stanford.edu (Ben Pfaff) - 2012-01-17 15:32 -0800
            Re: Writing "absolutely" portable code Kaz Kylheku <kaz@kylheku.com> - 2012-01-18 00:40 +0000
              Re: Writing "absolutely" portable code Seebs <usenet-nospam@seebs.net> - 2012-01-18 18:35 +0000
                Re: Writing "absolutely" portable code Kaz Kylheku <kaz@kylheku.com> - 2012-01-18 19:15 +0000
                Re: Writing "absolutely" portable code Seebs <usenet-nospam@seebs.net> - 2012-01-21 21:32 +0000
            Re: Writing "absolutely" portable code "io_x" <a@b.c.invalid> - 2012-01-18 07:26 +0100
              Re: Writing "absolutely" portable code "Joachim Schmitz" <nospam.jojo@schmitz-digital.de> - 2012-01-18 11:07 +0100
                Re: Writing "absolutely" portable code Seebs <usenet-nospam@seebs.net> - 2012-01-21 21:32 +0000
                Re: Writing "absolutely" portable code Ian Collins <ian-news@hotmail.com> - 2012-01-22 10:42 +1300
                Re: Writing "absolutely" portable code "io_x" <a@b.c.invalid> - 2012-01-22 18:53 +0100
                Re: Writing "absolutely" portable code "io_x" <a@b.c.invalid> - 2012-01-22 19:00 +0100
                Re: Writing "absolutely" portable code "io_x" <a@b.c.invalid> - 2012-01-23 19:28 +0100
              Re: Writing "absolutely" portable code Stephen Sprunk <stephen@sprunk.org> - 2012-01-18 08:44 -0600
              Re: Writing "absolutely" portable code James Dow Allen <jdallen2000@yahoo.com> - 2012-01-18 07:09 -0800
                Re: Writing "absolutely" portable code "io_x" <a@b.c.invalid> - 2012-01-18 17:44 +0100
        Re: Writing "absolutely" portable code Seebs <usenet-nospam@seebs.net> - 2012-01-18 07:58 +0000

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