target_environment() uses a temporary hash table for collecting exported variables from the sets.   This table uses variable_hash_1 and variable_hash_2 which expect the struct variable::length field to be correct and will generate incorrect values for the shell_var since its length field is 0.

The result is, for instance, that the last test in tests/scripts/variables/SHELL exports the wrong SHELL variable.

The fix is very simple, just initialize shell_var.length to 5 in main.c (line 1189 in r1.227).