bugmake - Bugs: bug #45476, cygwin: stderr redirect append...

 
 

bug #45476: cygwin: stderr redirect append does not work with native Windows programs

Submitter:  marco atzeri <matzeri>
Submitted:  Sun 05 Jul 2015 08:36:11 PM UTC
   
 
Severity:  3 - Normal Item Group:  Enhancement
Status:  None Privacy:  Public
Assigned to:  eliz Open/Closed:  Open
Component Version:  4.1 Operating System:  MS Windows
Fixed Release:  None Triage Status:  Need Info
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Wed 23 Sep 2015 09:25:34 AM UTC, comment #2: 

I'm changing the status of this to "Enhancement" because the example Makefile works as expected with native Windows shell and make and sort programs.

Eli Zaretskii <eliz>
Group Member
Mon 06 Jul 2015 07:38:05 PM UTC, comment #1: 


> redirecting stderr in append mode does not work if the program being invoked on a shell line is a native Windows executable. Instead of appending, the stderr output is written to the top of the file, corrupting it. This happens only if the 'make' process has its own stdout/err redirected to a pipe.


Isn't that an issue with how Cygwin libc implements invocation of subprocesses?  I'm guessing that the implementation of standard descriptors inheritance uses Cygwin-specific hooks, and this works only if the subprocess is a Cygwin program.  If this guess is correct, what would you like Make do in its upstream code to resolve this basic issue, which is really one aspect of incompatibility between Cywgin and native Windows programs?

Eli Zaretskii <eliz>
Group Member
Sun 05 Jul 2015 08:36:11 PM UTC, original submission:  

First reported at
https://cygwin.com/ml/cygwin/2015-05/msg00140.html

I was not able to bisect make code to identify when
the issue was introduced.
Attached test case

--- original message ----

Using 32-bit cygwin 2.0.2 and make 4.1-1, in a recipe, redirecting
stderr in append mode does not work if the program being invoked on a
shell line is a native Windows executable.  Instead of appending, the
stderr output is written to the top of the file, corrupting it. This
happens only if the 'make' process has its own stdout/err redirected to
a pipe.

Example recipe:

    all:
            echo first > output
            echo
secondxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx >> output
            /cygdrive/c/Windows/System32/sort.exe nonexist 2>> output; true

When "make" is run, the "output" file should be:

    first
    secondxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    nonexistThe system cannot find the file specified.

and in fact it is.  But when "make 2>&1 | cat" is run, the output is:

    nonexistThe system cannot find the file specified.
    xxxxxxxxxxxxxx

even though it should be the same as before.  The error message written
by sort.exe went to the top of the file instead of the end.

The problem does not happen if 'sort.exe' is replaced with a cygwin
program such as /usr/bin/sort.

The problem does not happen if stdout is redirected instead of stderr.

The problem does not happen if the output of 'make' is redirected to
a file instead of a pipe.

The problem does not happen if the sequence of commands in the recipe
is copied into a shell script and the shell invoked with its output
redirected to a pipe.  That is why I am filing this against 'make'.
However, it is possible the bug is in the shell (or a different shell?)
and I just don't know how to invoke it properly to imitate what 'make'
does.

I am attaching a reproducer Makefile.  Run "make 2>&1 | cat" to see
the incorrect output:

    $ make 2>&1 | cat
    echo first > output
    echo secondxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx >>
output
    /cygdrive/c/Windows/System32/sort.exe nonexist 2>> output; true
    ----- BEGIN output -----
    nonexistThe system cannot find the file specified.
    xxxxxxxxxxxxxx
    ----- END output -----

The bug happens with both make 4.1 and make 4.0 on cygwin 2.0.2.  It
does not happen with make 3.82.90 and cygwin 1.7.23.

marco atzeri <matzeri>

 

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Attach Files:
   
   
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Attached Files
file #34383:  Makefile added by matzeri (293B - application/octet-stream)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-09-23 eliz Item GroupBug Enhancement
        Assigned toNone eliz
        Triage StatusNone Need Info
    2015-07-05 matzeri Attached File- Added Makefile, #34383

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