m4sh bug (AS_VAR_IF)

[Randall Cotton]

On Ubuntu 9.04, with autoconf installed from repository:

$ autoconf --version
autoconf (GNU Autoconf) 2.63
[text deleted]

(NOTE: this problem is still present in 2.67)

Here is the definition for AS_VAR_IF in m4sugar/m4sh.m4:

----------- snip here --------------
# AS_VAR_IF(VARIABLE, VALUE, IF-TRUE, IF-FALSE)
# ---------------------------------------------
# Implement a shell `if test $VARIABLE = VALUE; then-else'.
# Polymorphic, and avoids sh expansion error upon interrupt or term signal.
m4_define([AS_VAR_IF],
[AS_LITERAL_IF([$1],
  [AS_IF([test "x$$1" = x""$2], [$3], [$4])],
  [as_val=AS_VAR_GET([$1])
   AS_IF([test "x$as_val" = x""$2], [$3], [$4])])])
----------- snip here --------------


The bug is located...

  [AS_IF([test "x$$1" = x""$2], [$3], [$4])],
                 ...here ^^^^
   AS_IF([test "x$as_val" = x""$2], [$3], [$4])])])
                 ...AND here ^^^^ 

It seems likely that x""$2 was meant to be "x$2".

The bug in action:

$ cat m4shtest.m4sh
AS_INIT
testvar="blah blah"
indirecttestvar=testvar
printf "Testing with literal variable name\n"
AS_VAR_IF([testvar], [blah blah], [printf "compare OK\n"], [printf "compare
failed\n"])
printf "Testing with indirect variable name\n"
AS_VAR_IF([$indirecttestvar], [blah blah], [printf "compare OK\n"], [printf
"compare failed\n"])
$ autom4te -l m4sh <m4shtest.m4sh >m4shtest.sh
$ sh m4shtest.sh
Testing with literal variable name
test: 431: xblah: unexpected operator
compare failed
Testing with indirect variable name
test: 440: xblah: unexpected operator
compare failed
$ cat -n m4shtest.sh |tail --lines +423
   423  
   424  testvar="blah blah"
   425  indirecttestvar=testvar
   426  printf "Testing with literal variable name\n"
   427  if test "x$testvar" = x""blah blah; then
   428    printf "compare OK\n"
   429  else
   430    printf "compare failed\n"
   431  fi
   432  
   433  printf "Testing with indirect variable name\n"
   434  as_val=`eval 'as_val=${'$indirecttestvar'}
   435                   $as_echo "$as_val"'`
   436     if test "x$as_val" = x""blah blah; then
   437    printf "compare OK\n"
   438  else
   439    printf "compare failed\n"
   440  fi
   441  
$ 

A workaround would be to shell-quote the second argument to AS_VAR_IF, as
in:
AS_VAR_IF([testvar], ["blah blah"], [printf "compare OK\n"], [printf "compare

But the documentation makes no mention that this is required. Furthermore,
it seems unnecessary to inflict such a requirement. Instead, if the double
quotes were rearranged as it seems they were originally meant...

$ cat m4shtestfix.m4sh
AS_INIT
dnl 08/16/10 REC (14:48:20) Redefine AS_VAR_IF to fix bug:
m4_define([AS_VAR_IF],
[AS_LITERAL_IF([$1],
  [AS_IF([test "x$$1" = "x$2"], [$3], [$4])],
  [as_val=AS_VAR_GET([$1])
   AS_IF([test "x$as_val" = "x$2"], [$3], [$4])])])dnl
testvar="blah blah"
indirecttestvar=testvar
printf "Testing with literal variable name\n"
AS_VAR_IF([testvar], [blah blah], [printf "compare OK\n"], [printf "compare
failed\n"])
printf "Testing with indirect variable name\n"
AS_VAR_IF([$indirecttestvar], [blah blah], [printf "compare OK\n"], [printf
"compare failed\n"])
$ autom4te -l m4sh <m4shtestfix.m4sh >m4shtestfix.sh
$ sh ./m4shtestfix.sh
Testing with literal variable name
compare OK
Testing with indirect variable name
compare OK
$ cat -n m4shtestfix.sh |tail --lines +423
   423  
   424  testvar="blah blah"
   425  indirecttestvar=testvar
   426  printf "Testing with literal variable name\n"
   427  if test "x$testvar" = "xblah blah"; then
   428    printf "compare OK\n"
   429  else
   430    printf "compare failed\n"
   431  fi
   432  
   433  printf "Testing with indirect variable name\n"
   434  as_val=`eval 'as_val=${'$indirecttestvar'}
   435                   $as_echo "$as_val"'`
   436     if test "x$as_val" = "xblah blah"; then
   437    printf "compare OK\n"
   438  else
   439    printf "compare failed\n"
   440  fi
   441  
$ 

....Then all is well.

Randall Cotton