Makefile appears broken - touching header causes no build

[vsajip]

BPO	38264
Nosy	@vsajip

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-09-24.17:56:57.466>
labels = ['3.8', 'type-bug', '3.7', '3.9', 'build']
title = 'Makefile appears broken - touching header causes no build'
updated_at = <Date 2019-09-24.17:58:39.383>
user = 'https://github.com/vsajip'

bugs.python.org fields:

activity = <Date 2019-09-24.17:58:39.383>
actor = 'vinay.sajip'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Build']
creation = <Date 2019-09-24.17:56:57.466>
creator = 'vinay.sajip'
dependencies = []
files = []
hgrepos = []
issue_num = 38264
keywords = []
message_count = 2.0
messages = ['353105', '353106']
nosy_count = 1.0
nosy_names = ['vinay.sajip']
pr_nums = []
priority = 'high'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38264'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[vsajip]

There appears to be a failure in the Makefile build logic. Steps to reproduce:

1. Make a fresh build using "make clean && make"
2. run "touch Modules/_io/_iomodule.h"
3. Run "make" again.

Observed result: No related files get built.
Expected result: The directly including compilation units Modules/_io/{_iomodule,iobase,fileio,bufferedio,textio,bytesio,stringio}.o should be built. The compilation units which depend on these (e.g. Modules/textio.o) should also be built.

The problem appears to be related to Modules/makesetup, which adds rules to tbe Makefile. An example of a rule is

Modules/textio.o: $(srcdir)/Modules/_io/textio.c; $(CC) $(PY_BUILTIN_MODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN -I$(srcdir)/Include/internal -I$(srcdir)/Modules/_io -c $(srcdir)/Modules/_io/textio.c -o Modules/textio.o

The problem here looks like the lack of a dependency between Modules/_io/textio.o and Modules/_io/textio.o - there is only a dependency on Modules/_io/textio.c, which wouldn't be rebuilt on a touch of Modules/_io/_iomodule.h.

[vsajip]

Problem also seems to occur in 3.8 and 3.7.

[crazymerlyn]

Should this be closed? Looks like a duplicate of #89758 which has been fixed. I can't reproduce it on HEAD.

[itamaro]

closing. please reopen (or submit a new issue) if the issue can be reproduced on main branch.