[Bug tools/23173] New: eu-addr2line does not flush its output, causing problems when used from a script

[Bug tools/23173] New: eu-addr2line does not flush its output, causing problems when used from a script

[luke at diamand dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=23173

            Bug ID: 23173
           Summary: eu-addr2line does not flush its output, causing
                    problems when used from a script
           Product: elfutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: tools
          Assignee: unassigned at sourceware dot org
          Reporter: luke at diamand dot org
                CC: elfutils-devel at sourceware dot org
  Target Milestone: ---

I noticed that eu-addr2line just write its output to stdout without any
flushing.

That means that if you are using it in a pipe (in my case from Python) feeding
addresses to stdin one at a time, you won't get any output for quite some time.

Just adding a call to fflush(stdout) fixes the problem.

I noticed that the binutils addr2line utility does exactly this:

      /* fflush() is essential for using this command as a server
         child process that reads addresses from a pipe and responds
         with line number information, processing one address at a
         time.  */
      fflush (stdout);

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[Bug tools/23173] eu-addr2line does not flush its output, causing problems when used from a script

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=23173

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at klomp dot org
           Assignee|unassigned at sourceware dot org   |mark at klomp dot org

--- Comment #1 from Mark Wielaard <mark at klomp dot org> ---
Created attachment 11013
  --> https://sourceware.org/bugzilla/attachment.cgi?id=11013&action=edit
addr2line: Add explicit fflush for stdout when reading from stdin.

That sounds like a good idea. This patch does just that.

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[Bug tools/23173] eu-addr2line does not flush its output, causing problems when used from a script

[luke at diamand dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=23173

Luke Diamand <luke at diamand dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Luke Diamand <luke at diamand dot org> ---
That works like a charm with my Python test code:


#!/usr/bin/python3

import subprocess
import os

addr = b'0xa6308\n'
elf = 'myfile.elf'

a2l='eu-addr2line'
p = subprocess.Popen([a2l, '-f', '--demangle', '-e', elf],
        stdin=subprocess.PIPE, stdout=subprocess.PIPE)

p.stdin.write(addr)
p.stdin.flush()
print(p.stdout.readline())
print(p.stdout.readline())

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