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Subject: bug#21309: libtool generates binary data in config.log due to buggy escaping
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I've reported the following bug in the Debian BTS:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=3D796180

but I can reproduce it with the official libtool 2.4.6.

When I run "./configure" with MPFR, the generated config.log file
contains binary data:

configure:9458: /usr/bin/nm -B conftest.o \| sed -n -e 's/^.*[ ]\([ABCDGI=
RSTW][ABCDGIRSTW]*\)[ ][ ]*\([_A-Za-z][_A-Za-z0-9]*\)$/^A ^B ^B/p' | sed =
'/ __gnu_lto/d' \> conftest.nm

where ^A and ^B are the ASCII characters of code 1 and 2 respectively.
Thus, the "file" utility thinks that this is a binary file, so that
"less" + "lesspipe" mangles the file. Rather annoying!

The generated "libtool" script contains:

global_symbol_pipe=3D"sed -n -e 's/^.*[    ]\\([ABCDGIRSTW][ABCDGIRSTW]*\=
\)[       ][      ]*\\([_A-Za-z][_A-Za-z0-9]*\\)\$/\\1 \\2 \\2/p' | sed '=
/ __gnu_lto/d'"

So, I suppose that the binary data come from the \\1 and \\2.

--=20
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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To: Vincent Lefevre <vincent@HIDDEN>
Subject: bug#21309: Acknowledgement (libtool generates binary data in
 config.log due to buggy escaping)
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Subject: bug#21309: libtool generates binary data in config.log due to buggy escaping
Resent-From: Vincent Lefevre <vincent@HIDDEN>
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Date: Mon, 8 Feb 2016 17:44:39 +0100
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I actually get these binary data with dash (when setting
CONFIG_SHELL=/bin/sh in my environment, where /bin/sh is dash).

On 2015-08-20 03:56:02 +0200, Vincent Lefevre wrote:
> The generated "libtool" script contains:
> 
> global_symbol_pipe="sed -n -e 's/^.*[    ]\\([ABCDGIRSTW][ABCDGIRSTW]*\\)[       ][      ]*\\([_A-Za-z][_A-Za-z0-9]*\\)\$/\\1 \\2 \\2/p' | sed '/ __gnu_lto/d'"
> 
> So, I suppose that the binary data come from the \\1 and \\2.

The problem is that it yields, for instance:

+ echo configure:10030: /usr/bin/nm -B conftest.o \| sed -n -e 's/^.*[ ]\([ABCDGIRSTW][ABCDGIRSTW]*\)[ ][ ]*\([_A-Za-z][_A-Za-z0-9]*\)$/\1 \2 \2/p' | sed '/ __gnu_lto/d' \> conftest.nm

With bash:

$ echo '\1' | hd
00000000  5c 31 0a                                          |\1.|
00000003

With dash:

$ echo '\1' | hd
00000000  01 0a                                             |..|
00000002

POSIX[*] says:

  if any of the operands contain a <backslash> character, the results
  are implementation-defined.

So, the above code is not portable.

[*] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html

-- 
Vincent Lef�vre <vincent@HIDDEN> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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Subject: bug#21309: libtool generates binary data in config.log due to buggy escaping
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Date: Tue, 2 Oct 2018 11:12:52 +0200
From: Vincent Lefevre <vincent@HIDDEN>
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On 2016-02-08 17:44:39 +0100, Vincent Lefevre wrote:
> I actually get these binary data with dash (when setting
> CONFIG_SHELL=/bin/sh in my environment, where /bin/sh is dash).
> 
> On 2015-08-20 03:56:02 +0200, Vincent Lefevre wrote:
> > The generated "libtool" script contains:
> > 
> > global_symbol_pipe="sed -n -e 's/^.*[    ]\\([ABCDGIRSTW][ABCDGIRSTW]*\\)[       ][      ]*\\([_A-Za-z][_A-Za-z0-9]*\\)\$/\\1 \\2 \\2/p' | sed '/ __gnu_lto/d'"
> > 
> > So, I suppose that the binary data come from the \\1 and \\2.
> 
> The problem is that it yields, for instance:
> 
> + echo configure:10030: /usr/bin/nm -B conftest.o \| sed -n -e 's/^.*[ ]\([ABCDGIRSTW][ABCDGIRSTW]*\)[ ][ ]*\([_A-Za-z][_A-Za-z0-9]*\)$/\1 \2 \2/p' | sed '/ __gnu_lto/d' \> conftest.nm

More details (with the current MPFR trunk, thus this has changed
a bit):

[...]
+ nlist=conftest.nm
+ eval echo "$as_me":7267: "/usr/bin/nm -B conftest.o \| sed -n -e 's/^.*[ ]\([A
BCDGIRSTW][ABCDGIRSTW]*\)[ ][ ]*\([_A-Za-z][_A-Za-z0-9]*\)$/\1 \2 \2/p' | sed '/ __gnu_lto/d' \> conftest.nm"
+ echo configure:7267: /usr/bin/nm -B conftest.o \| sed -n -e 's/^.*[ ]\([ABCDGIRSTW][ABCDGIRSTW]*\)[ ][ ]*\([_A-Za-z][_A-Za-z0-9]*\)$/\1 \2 \2/p' | sed '/ __gnu_lto/d' \> conftest.nm
[...]

In libtool.m4, this corresponds to:

    nlist=conftest.nm
    if AC_TRY_EVAL(NM conftest.$ac_objext \| "$lt_cv_sys_global_symbol_pipe" \> $nlist) && test -s "$nlist"; then

Thus the problem seems to come from AC_TRY_EVAL, i.e. an autoconf bug.

According to https://debbugs.gnu.org/Packages.html, autoconf doesn't
use this bug tracker, so that I'm going to report a separate bug for
autoconf.

-- 
Vincent Lef�vre <vincent@HIDDEN> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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retitle 21309 libtool should not use the dangerous, undocumented AC_TRY_EVAL macro, currently broken
thanks

On 2018-10-02 11:12:52 +0200, Vincent Lefevre wrote:
> In libtool.m4, this corresponds to:
> 
>     nlist=conftest.nm
>     if AC_TRY_EVAL(NM conftest.$ac_objext \| "$lt_cv_sys_global_symbol_pipe" \> $nlist) && test -s "$nlist"; then
> 
> Thus the problem seems to come from AC_TRY_EVAL, i.e. an autoconf bug.

I've seen in the autoconf source that AC_TRY_EVAL should not be used:

# AC_TRY_EVAL(VARIABLE)
# ---------------------
# Evaluate $VARIABLE, which should be a valid shell command.
# The purpose of this macro is to write "configure:123: command line"
# into config.log for every test run.
#
# The AC_TRY_EVAL and AC_TRY_COMMAND macros are dangerous and
# undocumented, and should not be used.
# They may be removed or their API changed in a future release.
# Autoconf itself no longer uses these two macros; they are present
# only for backward compatibility with previous versions of Autoconf.
# Not every shell command will work due to problems with eval
# and quoting, and the rules for exactly what does work are tricky.
# Worse, due to double-expansion during evaluation, arbitrary unintended
# shell commands could be executed in some situations.

-- 
Vincent Lef�vre <vincent@HIDDEN> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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Subject: Re: libtool generates binary data in config.log due to buggy escaping
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retitle 21309 libtool should not use the dangerous, undocumented AC_TRY_EVAL macro, currently broken
thanks

On 2018-10-02 11:12:52 +0200, Vincent Lefevre wrote:
> In libtool.m4, this corresponds to:
> 
>     nlist=conftest.nm
>     if AC_TRY_EVAL(NM conftest.$ac_objext \| "$lt_cv_sys_global_symbol_pipe" \> $nlist) && test -s "$nlist"; then
> 
> Thus the problem seems to come from AC_TRY_EVAL, i.e. an autoconf bug.

I've seen in the autoconf source that AC_TRY_EVAL should not be used:

# AC_TRY_EVAL(VARIABLE)
# ---------------------
# Evaluate $VARIABLE, which should be a valid shell command.
# The purpose of this macro is to write "configure:123: command line"
# into config.log for every test run.
#
# The AC_TRY_EVAL and AC_TRY_COMMAND macros are dangerous and
# undocumented, and should not be used.
# They may be removed or their API changed in a future release.
# Autoconf itself no longer uses these two macros; they are present
# only for backward compatibility with previous versions of Autoconf.
# Not every shell command will work due to problems with eval
# and quoting, and the rules for exactly what does work are tricky.
# Worse, due to double-expansion during evaluation, arbitrary unintended
# shell commands could be executed in some situations.

-- 
Vincent Lef�vre <vincent@HIDDEN> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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On 2018-10-02 12:58:04 +0200, Vincent Lefevre wrote:
> I've seen in the autoconf source that AC_TRY_EVAL should not be used:
> 
> # AC_TRY_EVAL(VARIABLE)
> # ---------------------
> # Evaluate $VARIABLE, which should be a valid shell command.
> # The purpose of this macro is to write "configure:123: command line"
> # into config.log for every test run.
> #
> # The AC_TRY_EVAL and AC_TRY_COMMAND macros are dangerous and
> # undocumented, and should not be used.
> # They may be removed or their API changed in a future release.
> # Autoconf itself no longer uses these two macros; they are present
> # only for backward compatibility with previous versions of Autoconf.
> # Not every shell command will work due to problems with eval
> # and quoting, and the rules for exactly what does work are tricky.
> # Worse, due to double-expansion during evaluation, arbitrary unintended
> # shell commands could be executed in some situations.

I've attached a patch that replaces the AC_TRY_EVAL occurrence that
generated the binary data. This is a patch against the Debian package
(libtool 2.4.6-4). I've tested it with MPFR and it seems to work fine.

The other AC_TRY_EVAL occurrences do not cause any problem here,
but should also be replaced in the future.

For the reference, my Debian bug report (clone of 796180, which is
now about autoconf):

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=910076

-- 
Vincent Lef�vre <vincent@HIDDEN> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

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Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename="libtool-eval-nm.patch"

Description: Avoid a broken AC_TRY_EVAL macro
 As said in the Autoconf source, the AC_TRY_EVAL macro is dangerous and
 undocumented, and should not be used.
 In particular, the one related to nm yields binary data in the config.log
 file with dash, where "echo \\1" (echo with the argument \1) produces the
 control character ^A instead of the usual \1 with most shells (POSIX says
 that the result is implementation-defined). See:
   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=910076
 This patch attempts to replace this AC_TRY_EVAL occurrence by code with
 similar behavior, but using $ECHO instead of echo in order to avoid the
 backslash issue.
Author: Vincent Lefevre <vincent@HIDDEN>
Last-Updated: 2018-10-02

Index: libtool-2.4.6/m4/libtool.m4
===================================================================
--- libtool-2.4.6.orig/m4/libtool.m4
+++ libtool-2.4.6/m4/libtool.m4
@@ -4063,7 +4063,8 @@ _LT_EOF
   if AC_TRY_EVAL(ac_compile); then
     # Now try to grab the symbols.
     nlist=conftest.nm
-    if AC_TRY_EVAL(NM conftest.$ac_objext \| "$lt_cv_sys_global_symbol_pipe" \> $nlist) && test -s "$nlist"; then
+    $ECHO "$as_me:$LINENO: $NM conftest.$ac_objext | $lt_cv_sys_global_symbol_pipe > $nlist" >&AS_MESSAGE_LOG_FD
+    if eval "$NM" conftest.$ac_objext \| "$lt_cv_sys_global_symbol_pipe" \> $nlist 2>&AS_MESSAGE_LOG_FD && test -s "$nlist"; then
       # Try sorting and uniquifying the output.
       if sort "$nlist" | uniq > "$nlist"T; then
 	mv -f "$nlist"T "$nlist"

--OXfL5xGRrasGEqWY--

Last modified: Mon, 25 Nov 2019 12:00:02 UTC

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