From d0f104991b9e6134f04bc674af115bc288c9e137 Mon Sep 17 00:00:00 2001
From: Jacob Bachmeyer <jcb@gnu.org>
Date: Fri, 16 Apr 2021 16:34:56 -0500
Subject: Allow environment to specify a shell for running config.guess

---
 ChangeLog   |  6 ++++++
 runtest.exp | 51 +++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index bfc175c..bd0955e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,12 @@
 	* configure.ac: Remove experimental support for propagating
 	CONFIG_SHELL to scripts in the source directory.
 
+	* runtest.exp: Use CONFIG_SHELL or SHELL environment variable when
+	running config.guess.  Check the result carefully and stop with an
+	error immediately if running config.guess does not produce
+	something that plausibly resembles a triplet.  Advise the user
+	that SHELL or CONFIG_SHELL may need to be set in the environment.
+
 2021-04-15  Jacob Bachmeyer  <jcb@gnu.org>
 
 	PR47382
diff --git a/runtest.exp b/runtest.exp
index 3220485..93ae2ab 100644
--- a/runtest.exp
+++ b/runtest.exp
@@ -823,13 +823,52 @@ if {[expr {$build_triplet eq "" && $host_triplet eq ""}]} {
 	send_error "ERROR: Couldn't find config.guess program.\n"
 	exit 1
     }
-    catch "exec $config_guess" build_triplet
-    switch -- $build_triplet {
-	"No uname command or uname output not recognized" -
-	"Unable to guess system type" {
-	    verbose "WARNING: Uname output not recognized"
-	    set build_triplet unknown
+    if { [info exists ::env(CONFIG_SHELL)] } {
+	if { [catch {exec $::env(CONFIG_SHELL) $config_guess} build_triplet] } {
+	    if { [lindex $::errorCode 0] eq "CHILDSTATUS" } {
+		send_error "ERROR: Running config.guess with\
+					CONFIG_SHELL=$::env(CONFIG_SHELL)\
+					exited on code\
+					[lindex $::errorCode 2].\n"
+	    } else {
+		send_error "ERROR: Running config.guess with\
+					CONFIG_SHELL=$::env(CONFIG_SHELL)\
+					produced error:\n"
+		send_error "        $::errorCode\n"
+	    }
+	}
+    } elseif { [info exists ::env(SHELL)] } {
+	if { [catch {exec $::env(SHELL) $config_guess} build_triplet] } {
+	    if { [lindex $::errorCode 0] eq "CHILDSTATUS" } {
+		send_error "ERROR: Running config.guess with\
+					SHELL=$::env(SHELL)\
+					exited on code\
+					[lindex $::errorCode 2].\n"
+	    } else {
+		send_error "ERROR: Running config.guess with\
+					SHELL=$::env(SHELL)\
+					produced error:\n"
+		send_error "        $::errorCode\n"
+	    }
 	}
+    } else {
+	if { [catch {exec $config_guess} build_triplet] } {
+	    if { [lindex $::errorCode 0] eq "CHILDSTATUS" } {
+		send_error "ERROR: Running config.guess exited on code\
+					[lindex $::errorCode 2].\n"
+	    } else {
+		send_error "ERROR: Running config.guess produced error:\n"
+		send_error "        $::errorCode\n"
+	    }
+	}
+    }
+    if { ![regexp -- {^[^-]+-[^-]+-[^-]+} $build_triplet] } {
+	send_error "ERROR: Running config.guess produced bogus build triplet:\n"
+	send_error "        $build_triplet\n"
+	send_error "       (Perhaps you need to set CONFIG_SHELL or\
+				SHELL in your environment\n"
+	send_error "        to the absolute file name of a POSIX shell?)\n"
+	exit 1
     }
     verbose "Assuming build host is $build_triplet"
     if { $host_triplet eq "" } {
-- 
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