Ndtyjky

I'm trying to test if ANDROID_NDK_ROOT is set in an Autoconf script. The relevant stanza is shown below. According to How can I check an environment variable? on the Autoconf mailing list, I can use:

if test "${var+set}" = set; then

  echo "variable $var is set to: $var"

fi 

The variable is not set, but my AC_MSG_ERROR is not being executed.

$ printenv | grep ANDROID_NDK_ROOT

$

Instead, the test is producing the following error:

./configure: line 20616: syntax error near unexpected token `('

./configure: line 20616: `  $as_echo_n "(cached) " >&6'

(There's another reply in the thread but it seems to be just a comment and does not answer the question).

How do I test if an environmental variable is set in Autoconf?

Here is the stanza I am trying to execute in configure.ac:

# if test "$IS_ANDROID_OS" != "0"; then

if true; then



   if test "${ANDROID_NDK_ROOT+set}" != set; then

     AC_MSG_ERROR([ANDROID_NDK_ROOT is not set. Please set ANDROID_NDK_ROOT])

   fi 



   THIS_FILE="$ANDROID_NDK_ROOT/sources/android/cpufeatures/cpu-features.h"

   AC_CHECK_FILE([$THIS_FILE],

      [cp "$THIS_FILE" "$ac_srcdir"],

      AC_MSG_RESULT([cpu-features.h does not exist in ANDROID_NDK_ROOT, skipping])

   )



   THIS_FILE="$ANDROID_NDK_ROOT/sources/android/cpufeatures/cpu-features.c"

   AC_CHECK_FILE([$THIS_FILE],

      [cp "$THIS_FILE" "$ac_srcdir"],

      AC_MSG_RESULT([cpu-features.c does not exist in ANDROID_NDK_ROOT, skipping])

   )

fi

Here is the chunk of configure from cat -n:

 20610

 20611     THIS_FILE="$ANDROID_NDK_ROOT/sources/android/cpufeatures/cpu-features.c"

 20612     as_ac_File=`$as_echo "ac_cv_file_$THIS_FILE" | $as_tr_sh`

 20613  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $THIS_FILE" >&5

 20614  $as_echo_n "checking for $THIS_FILE... " >&6; }

 20615  if eval ${$as_ac_File+:} false; then :

 20616    $as_echo_n "(cached) " >&6

 20617  else

 20618    test "$cross_compiling" = yes &&

 20619    as_fn_error $? "cannot check for file existence when cross compiling""$LINENO" 5

 20620  if test -r "$THIS_FILE"; then

 20621    eval "$as_ac_File=yes"

 20622  else

 20623    eval "$as_ac_File=no"

 20624  fi

There's nothing wrong with your shell syntax for testing whether a variable is set, and it works fine with Autoconf.

The problem appears to arise from failing to quote the third arguments to the AC_CHECK_FILE() macros. You should always quote (with square brackets) each argument to each macro, especially when that argument is or contains a macro call itself. I can reproduce a syntax error in configure by wrapping the example code you provided between an AC_INIT and an AC_OUTPUT, but it goes away with proper quoting. Specifically, here:

   THIS_FILE="$ANDROID_NDK_ROOT/sources/android/cpufeatures/cpu-features.h"

   AC_CHECK_FILE([$THIS_FILE],

      [cp "$THIS_FILE" "$ac_srcdir"],

      [AC_MSG_RESULT([cpu-features.h does not exist in ANDROID_NDK_ROOT, skipping])]

   )



   THIS_FILE="$ANDROID_NDK_ROOT/sources/android/cpufeatures/cpu-features.c"

   AC_CHECK_FILE([$THIS_FILE],

      [cp "$THIS_FILE" "$ac_srcdir"],

      [AC_MSG_RESULT([cpu-features.c does not exist in ANDROID_NDK_ROOT, skipping])]

   )

Failing to quote the argument results in it being expanded too many times, and the resulting output indeed is not syntactically valid shell code.