Programs differing only by ".exe" suffix: subtle Libtool 1.3 +Automake 1.4 interaction bug

["Matthew D. Langston" <langston@SLAC.Stanford.EDU>]

This tiny package, "lt_am_bug", demonstrates a subtle bug that was
introduced in Libtool 1.3 concerning the interaction of Libtool 1.3 with
Automake 1.4.  The bug can be enabled by passing the flag "--enable-bug"
to `configure'.  By default the bug is disabled.

The bug was discovered on a system with x86 Linux (Pentium III, Linux
2.0.36, glibc 2.0.7, i686-pc-linux-gnu) with Autoconf 2.13 and Automake
1.4.  It appeared after upgrading from Libtool 1.2 to Libtool 1.3.  The
bug is not present when using Libtool 1.2 with Automake 1.4.

In a nutshell, an Automake/Libtool package becomes "broken" when two
programs (i.e. in some Automake "_PROGRAMS" primary) differ in their
names only by the suffix ".exe".  For example, the following snippet
from `Makefile.am' works as expected:

  bin_PROGRAMS     = main main.exx
  main_exx_SOURCES = main2.c
  main_exx_LDADD   = libtest.la

In this case two programs will be created, `main' and `main.exx'.
Please see `Makefile.am' (a tiny file) for the full context.  This
produces the following (correct) output from "make check".

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
                       begin "make check" output
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
  $ make check
  make  check-TESTS
  make[1]: Entering directory `/mnt/hdc/projects/sourceware/build/lt_am_bug'
  Hello from ./main
  PASS: main
  Hello from lt-main.exx
  Hello from the test library
  PASS: main.exx
  ==================
  All 2 tests passed
  ==================
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
                        end "make check" output
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


However, making the following change to `Makefile.am' (replacing the 3
occurrences of "exx" with "exe") will demonstrate the bug:


  bin_PROGRAMS     = main main.exe
  main_exe_SOURCES = main2.c
  main_exe_LDADD   = libtest.la

In this case the two programs that should be created, `main' and
`main.exe', are not created.  Only the Libtool wrapper `main' is
created, which incorrectly wraps the nonexistent program
`.libs/main.exe'.  Again, please see `Makefile.am' for the full context.
This produces the following (incorrect) output from "make check".


<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
                       begin "make check" output
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
  $ make check
  /bin/sh ./libtool --mode=link gcc  -g -O2  -o main.exe  main2.o libtest.la 
  gcc -g -O2 -o .libs/main.exe main2.o .libs/libtest.so -Wl,--rpath -Wl,/usr/local/lib
  creating main.exe
  make  check-TESTS
  make[1]: Entering directory `/mnt/hdc/projects/sourceware/build/lt_am_bug'
  /bin/sh ./libtool --mode=link gcc  -g -O2  -o main.exe  main2.o libtest.la 
  gcc -g -O2 -o .libs/main.exe main2.o .libs/libtest.so -Wl,--rpath -Wl,/usr/local/lib
  creating main.exe
  Hello from lt-main.exe
  Hello from the test library
  PASS: main
  /bin/sh: ../../lt_am_bug-0.01/main.exe: No such file or directory
  FAIL: main.exe
  ===================
  1 of 2 tests failed
  ===================
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
                        end "make check" output
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Also notice that with the buggy version enabled, the program `main.exe'
is always recompiled and relinked, i.e. the dependency in the generated
Makefile is somehow wrong as well.

I don't know if the problem lies within Libtool 1.3 or Automake 1.4, but
the bug isn't present when using Libtool 1.2 with Automake 1.4.

I recently came across this bug while "Autoconfing" a package called
ROOT (an analysis package for High Energy Physics).  My "Autoconfed"
version of ROOT creates two programs named "root" and "root.exe".  Since
I am packaging a 3rd party package, I have no control over the names of
these two programs.  I have had to fall back to Libtool 1.2 for now.

--
Matthew D. Langston
SLD, Stanford Linear Accelerator Center
langston@SLAC.Stanford.EDU

lt_am_bug-0.01.tar.gz