Musl bug, or, am I losing my mind?

[Guided Muscle <atguarded-gizmo@yahoo.com>]

Houston, I think we have a problem.
I used musl-gcc to compile tinycdb on Debian 8 and kept getting errors on a very simple test case.

Make options:
CC=musl-gcc
CFLAGS=-O2 -s -static -fPIC -D_FILE_OFFSET_BITS=64 
The resulting executable is cdb.

Test data is generated via a lua script (test.lua):
for i=1,10000 do
  key,val="key" .. tostring(i), "value" .. string.rep(tostring(i),i)
  print(string.format("+%d,%d:%s->%s", string.len(key),string.len(val),key,val))
end
print("\n")

Running lua test.lua | cdb -c o.cdb always results in an error ... FAILED
cdb: (stdin): bad format

So, maybe they broke the pipe in Linux Debian ... Let's prepare a temporary file  lua test.lua > o.txt

The, run this puppy:
cat o.txt | cdb -c c.cdb  
FAILED: cdb: (stdin): bad format

However 
PASS: cdb -c c.cdb < o.txt

What am I missing?

Thanks
GM