Fix testsuite failures with bash 5.2.

Bash v5.2 includes several new optimizations to the number of
subshells used for various constructs; as a side effect, the value of
SHLVL is less stable than it used to be.  Add SHLVL to the list of
built-in shell variables with unstable values, to be ignored when
checking for inappropriate differences to the shell environment
before and after a macro invocation / between two configure runs.

Problem and solution reported by Xi Ruoyao in
https://lists.gnu.org/archive/html/autoconf/2022-09/msg00015.html
Problem also reported by Bruce Dubbs in
https://lists.gnu.org/archive/html/bug-autoconf/2022-09/msg00010.html

* tests/local.at (_AT_CHECK_ENV, AT_CONFIG_CMP): Ignore changes in
  value of SHLVL.
Copyright-paperwork-exempt: yes

diff --git a/tests/local.at b/tests/local.at
index 193fd11858725f649b1c2e627a7fb44dcf7d85ed..a9cf405037b775c57b8af6cb5d88acd1bbc0623a 100644 (file)
--- a/tests/local.at
+++ b/tests/local.at
@@ -352,7 +352,7 @@ m4_define([AT_CHECK_CONFIGURE],
 # - AC_SUBST'ed variables
 #   (FIXME: Generate a list of these automatically.)
 # - _|@|.[*#?$].|argv|ARGC|LINENO|OLDPWD|PIPESTATUS|RANDOM|SECONDS
-#   |START_TIME|ToD|_AST_FEATURES
+#   |SHLVL|START_TIME|ToD|_AST_FEATURES
 #   Some variables some shells use and change.
 #   '.[*#?$].' catches '$#' etc. which are displayed like this:
 #      | '!'=18186
@@ -404,7 +404,7 @@ if test -f state-env.before && test -f state-env.after; then
       [GREP|[EF]GREP|SED],
       [[_@]|.[*@%:@?$].],
       [argv|ARGC|LINENO|BASH_ARGC|BASH_ARGV|OLDPWD|PIPESTATUS|RANDOM],
-      [SECONDS|START_TIME|ToD|_AST_FEATURES]))=' \
+      [SECONDS|SHLVL|START_TIME|ToD|_AST_FEATURES]))=' \
      $act_file ||
        test $? -eq 1 || echo failed >&2
     ) 2>stderr-$act_file |
@@ -435,6 +435,7 @@ fi
 #   - PPID [bash, zsh]
 #   - RANDOM [bash, zsh]
 #   - SECONDS [bash, zsh]
+#   - SHLVL [bash]
 #   - START_TIME [NetBSD sh]
 #   - ToD [NetBSD sh]
 #   - '$' [zsh]
@@ -483,6 +484,7 @@ do
        /^PPID=/ d
        /^RANDOM=/ d
        /^SECONDS=/ d
+       /^SHLVL=/ d
        /^START_TIME=/ d
        /^ToD=/ d
        /'\'\\\$\''=/ d