gh-151814: Add test for TextIOWrapper.write unbounded memory growth from repeated writes

[cmaloney]

Use tracemalloc to measure memory usage.

Fails before GH-151817, passes after. Validated by changing condition between > 0 and >= 0 and rebuilding + running make && ./python -m test test_io.test_textio -m "test_write_empty_no_memory_growth".

cpython/Modules/_io/textio.c

Line 1823 in 908f438

if (bytes_len > 0) {

Inspired by the report memory usage helper in GH-152203 (If it gets more use should probably move to test.support).

cc: @StanFromIreland

• Issue: Runaway memory use when repeatedly printing empty string #151814

[StanFromIreland]

Inspired by the report memory usage helper in #152203

You're linking to a PR where they had to fix-up such a test, as such, I'm not convinced this is worth it.

[cmaloney]

In this case the allocations go on my machine from peak = 3067536 to peak = 0 blocks allocated. I think it's unlikely more allocations will happen in this empty global constant string write case. Even if we do add some new overheads with 200_000 iterations if we allocate 200_000 blocks probably worth making sure the change is intentional. Can up the constant further if worried about other overhead creep as the codebase evolves.