Fixed with test: Test bug #35820: sem breaks if $HOME is not writable

src/parallel

@@ -5000,9 +5000,9 @@ sub new {
     $id=~s/([^-_a-z0-9])/unpack("H*",$1)/ige; # Convert non-word chars to hex
     $id="id-".$id; # To distinguish it from a process id
     my $parallel_dir = $ENV{'HOME'}."/.parallel";
-    -d $parallel_dir or mkdir $parallel_dir;
+    -d $parallel_dir or mkdir_or_die($parallel_dir);
     my $parallel_locks = $parallel_dir."/semaphores";
-    -d $parallel_locks or mkdir $parallel_locks;
+    -d $parallel_locks or mkdir_or_die($parallel_locks);
     my $lockdir = "$parallel_locks/$id";
     my $lockfile = $lockdir.".lock";
     if($count < 1) { ::die_bug("semaphore-count: $count"); }
@@ -5082,7 +5082,7 @@ sub atomic_link_if_count_less_than {
     $self->lock();
     ::debug($self->nlinks()."<".$self->{'count'});
     if($self->nlinks() < $self->{'count'}) {
-	-d $self->{'lockdir'} || mkdir $self->{'lockdir'};
+	-d $self->{'lockdir'} or mkdir_or_die($self->{'lockdir'});
 	if(not -e $self->{'idfile'}) {
 	    open (A, ">", $self->{'idfile'}) or
 		::die_bug("write_idfile: $self->{'idfile'}");
@@ -5137,6 +5137,23 @@ sub unlock {
     ::debug("unlocked\n");
 }
 
+sub mkdir_or_die {
+    # If dir is not writable: die
+    my $dir = shift;
+    my @dir_parts = split(m:/:,$dir);
+    my ($ddir,$part);
+    while(defined ($part = shift @dir_parts)) {
+	$part eq "" and next;
+	$ddir .= "/".$part;
+	-d $ddir and next;
+	mkdir $ddir;
+    }
+    if(not -w $dir) {
+	print STDERR "$Global::progname: Cannot write to $dir: $!\n";
+	exit(255);
+    }
+}
+
 # Keep perl -w happy
 $::opt_x = $Semaphore::timeout = $Semaphore::wait = $::opt_shebang =
 0;

testsuite/tests-to-run/parallel-local150.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 echo '### Test fix #32191'
-seq 1 150 | parallel -j9 --retries 2 -S localhost,: "/bin/non-existant 2>/dev/null"
+seq 1 150 | nice nice parallel -j9 --retries 2 -S localhost,: "/bin/non-existant 2>/dev/null"
 
 echo '### Test --tagstring'
 parallel -j1 -X -v --tagstring a{}b echo  ::: 3 4
@@ -9,3 +9,9 @@ parallel -j1 -k -v --tagstring a{}b echo  ::: 3 4
 parallel -j1 -k -v --tagstring a{}b echo job{#} ::: 3 4
 parallel -j1 -k -v --tagstring ajob{#}b echo job{#} ::: 3 4
 
+echo '### Test bug #35820: sem breaks if $HOME is not writable'
+echo 'Workaround: use another writable dir'
+rm -rf /tmp/.parallel
+HOME=/tmp sem echo OK
+HOME=/tmp sem --wait
+HOME=/usr/this/should/fail stdout sem echo should fail

testsuite/wanted-results/parallel-local150

@@ -14,3 +14,7 @@ echo job1
 ajob1b	job1
 echo job2
 ajob2b	job2
+### Test bug #35820: sem breaks if $HOME is not writable
+Workaround: use another writable dir
+OK
+parallel: Cannot write to /usr/this/should/fail/.parallel: No such file or directory