Re: [BLOCKER] cannot single-step unit tests any more

[Jim Meyering]

Bruno Haible wrote:
> On a glibc system, I cannot single-step unit tests that are built upon
> tests/init.sh any more. This is blocking.
...
> Two things are wrong here:
> 1) If I'm already using bash, it MUST NOT do an 'exec', because that kills the
>    ability to do single-stepping.

Thanks for the report.

Besides, an unnecessary re-exec is simply wasteful.

Back when I wrote that code, I wanted to test the current shell before
any others, but my first attempt was not up to the task of accommodating
Solaris 10's twisted /bin/sh, so I stuck with the less efficient code
that worked.

Now I've tried harder, and this does the job:

>From cfa7f85bf1b1b1dcb51b27dc615f85e62710c056 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Sun, 16 May 2010 18:34:08 +0200
Subject: [PATCH] init.sh: avoid unnecessary shell re-exec

* tests/init.sh: Improve the re-exec-required check to first test the
current shell.  If it passes the test, do not search for a shell that
does pass, and do not re-exec.  This test is particularly contorted to
avoid triggering misbehavior in Solaris 10's /bin/sh whereby any use
of $(...) evokes a syntax error and causes immediate shell exit with
status 2.  Bruno Haible reported that the re-exec made it impossible
to single-step through any init.sh-using script.
---
 ChangeLog     |   11 +++++++++++
 tests/init.sh |   41 +++++++++++++++++++++++++++--------------
 2 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index c365994..ea50e39 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2010-05-16  Jim Meyering  <address@hidden>
+
+       init.sh: avoid unnecessary shell re-exec
+       * tests/init.sh: Improve the re-exec-required check to first test the
+       current shell.  If it passes the test, do not search for a shell that
+       does pass, and do not re-exec.  This test is particularly contorted to
+       avoid triggering misbehavior in Solaris 10's /bin/sh whereby any use
+       of $(...) evokes a syntax error and causes immediate shell exit with
+       status 2.  Bruno Haible reported that the re-exec made it impossible
+       to single-step through any init.sh-using script.
+
 2010-05-16  Bruno Haible  <address@hidden>

        Fix collision between gnulib's and libintl's printf replacements.
diff --git a/tests/init.sh b/tests/init.sh
index 05a983a..2ad385f 100644
--- a/tests/init.sh
+++ b/tests/init.sh
@@ -63,33 +63,46 @@
 # - hyphen-containing alias names
 # - we prefer to use ${var#...} substitution, rather than having
 #   to work around lack of support for that feature.
-# The following code attempts to find a shell with support for these features
-# and re-exec's it.  If not, it skips the current test.
+# The following code attempts to find a shell with support for these features.
+# If the current shell passes the test, we're done.  Otherwise, test other
+# shells until we find one that passes.  If one is found, re-exec it.
+# If no acceptable shell is found, skip the current test.
+#
+# Use "9" to indicate success (rather than 0), in case some shell acts
+# like Solaris 10's /bin/sh but exits successfully instead of with status 2.

 gl_shell_test_script_='
 test $(echo y) = y || exit 1
-test -z "$EXEEXT" && exit 0
+test -z "$EXEEXT" && exit 9
 shopt -s expand_aliases
 alias a-b="echo zoo"
 v=abx
      test ${v%x} = ab \
   && test ${v#a} = bx \
-  && test $(a-b) = zoo
+  && test $(a-b) = zoo \
+  && exit 9
 '

 if test "x$1" = "x--no-reexec"; then
   shift
 else
-  for re_shell_ in "${CONFIG_SHELL:-no_shell}" /bin/sh bash dash zsh pdksh fail
-  do
-    test "$re_shell_" = no_shell && continue
-    test "$re_shell_" = fail && skip_ failed to find an adequate shell
-    if "$re_shell_" -c "$gl_shell_test_script_" 2>/dev/null; then
-      exec "$re_shell_" "$0" --no-reexec "$@"
-      echo "$ME_: exec failed" 1>&2
-      exit 127
-    fi
-  done
+  # 'eval'ing the above code makes Solaris 10's /bin/sh exit with $? set to 2.
+  # It does not evaluate any of the code after the "unexpected" `('.  Thus,
+  # we must run it in a subshell.
+  ( eval "$gl_shell_test_script_" ) > /dev/null 2>&1
+  if test $? != 9; then
+    for re_shell_ in "${CONFIG_SHELL:-no_shell}" /bin/sh bash dash zsh pdksh 
fail
+    do
+      test "$re_shell_" = no_shell && continue
+      test "$re_shell_" = fail && skip_ failed to find an adequate shell
+      "$re_shell_" -c "$gl_shell_test_script_" 2>/dev/null
+      if test $? = 2; then
+        exec "$re_shell_" "$0" --no-reexec "$@"
+        echo "$ME_: exec failed" 1>&2
+        exit 127
+      fi
+    done
+  fi
 fi

 test -n "$EXEEXT" && shopt -s expand_aliases
--
1.7.1.250.g7d1e8