Make sure output is flushed before a read

I found this bug by a script I wrote to do aviation related stuff, a
script that would prompt for input without using newlines (because it
used `-P` in its hash-bang line).

1 files changed, 4 insertions, 0 deletions

diff --git a/src/program.c b/src/program.c
index d4e386d4..6ab79473 100644
--- a/src/program.c
+++ b/src/program.c
@@ -1928,6 +1928,10 @@ void bc_program_exec(BcProgram *p) {
 
 			case BC_INST_READ:
 			{
+				// We want to flush output before
+				// this in case there is a prompt.
+				bc_file_flush(&vm.fout);
+
 				bc_program_read(p);
 
 				ip = bc_vec_top(&p->stack);