In tree cross-build fails copying Include/graminit.h to itself

[moreati]

BPO	27229
Nosy	@doko42, @ned-deily, @xdegaye, @vadmium, @moreati
Files	graminit-same-file.patch vpath.patch

^{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 = <Date 2016-06-07.06:41:23.773>
created_at = <Date 2016-06-05.13:05:40.936>
labels = ['build']
title = 'In tree cross-build fails copying  Include/graminit.h to itself'
updated_at = <Date 2016-06-07.06:41:23.771>
user = 'https://github.com/moreati'

bugs.python.org fields:

activity = <Date 2016-06-07.06:41:23.771>
actor = 'martin.panter'
assignee = 'none'
closed = True
closed_date = <Date 2016-06-07.06:41:23.773>
closer = 'martin.panter'
components = ['Cross-Build']
creation = <Date 2016-06-05.13:05:40.936>
creator = 'Alex.Willmer'
dependencies = []
files = ['43235', '43249']
hgrepos = []
issue_num = 27229
keywords = ['patch']
message_count = 7.0
messages = ['267417', '267431', '267480', '267497', '267576', '267579', '267599']
nosy_count = 6.0
nosy_names = ['doko', 'ned.deily', 'xdegaye', 'python-dev', 'martin.panter', 'Alex.Willmer']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue27229'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6']

[moreati]

While trying a cross compile of Python 3.6 I encountered the following

alex@martha:~/src/cpython default☿ hg summary
parent: 101753:31ad7885e2e5
Issue bpo-27225: Fixed a reference leak in type_new when setting __new__ fails.
branch: default
commit: (clean)
update: (current)

alex@martha:/src/cpython default☿ ./configure --build=x86_64-linux --host=arm-linux-gnueabihf --disable-ipv6 ac_cv_file__dev_ptc=no ac_cv_file__dev_ptmx=no
checking for hg... found
...
creating Makefile
alex@martha:/src/cpython default☿ make
...
arm-linux-gnueabihf-gcc -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes Parser/acceler.o Parser/grammar1.o Parser/listnode.o Parser/node.o Parser/parser.o Parser/bitset.o Parser/metagrammar.o Parser/firstsets.o Parser/grammar.o Parser/pgen.o Objects/obmalloc.o Python/dynamic_annotations.o Python/mysnprintf.o Python/pyctype.o Parser/tokenizer_pgen.o Parser/printgrammar.o Parser/parsetok_pgen.o Parser/pgenmain.o -lpthread -ldl -lpthread -lutil -o Parser/pgen
if test "yes" != "yes"; then \
Parser/pgen ./Grammar/Grammar Include/graminit.h Python/graminit.c; \
else \
cp ./Include/graminit.h Include/graminit.h; \
fi
cp: './Include/graminit.h' and 'Include/graminit.h' are the same file
Makefile:806: recipe for target 'Include/graminit.h' failed
make: *** [Include/graminit.h] Error 1

The attached patch allows me to get past this error. I'm unsure if it's an appropriate fix or just a workaround.

[ned-deily]

The culprit appears to be the changes introduced for bpo-22359 (c36b9ef8ff39 and friends).

[xdegaye]

Yes, those changes incorrectly assume that the source directory and the build directory are always different (using VPATH). Alex patch LGTM, this other patch overwrites the graminit.[ch] files, not sure if this is better.

[vadmium]

I was a little concerned that Alex’s patch used “test A -ef B”, which is not specified by Posix. But it is apparently widely supported (and consider we would only need it for cross compilation). Anyway, I was going to suggest test "$(srcdir)" == "." instead, but maybe Xavier’s solution is slightly better again.

I say go with vpath.patch, perhaps with a brief comment explaining that the cp + mv dance avoids copying the file onto itself when doing an in-tree build.

[python-dev]

New changeset 619f7a2aa40a by Martin Panter in branch '3.5':
Issue bpo-27229: Fix in-tree cross-build rule, by Xavier de Gaye
https://hg.python.org/cpython/rev/619f7a2aa40a

New changeset 9902230b101f by Martin Panter in branch 'default':
Issue bpo-27229: Merge cross-compiling fix from 3.5
https://hg.python.org/cpython/rev/9902230b101f

New changeset ffed402528c7 by Martin Panter in branch '2.7':
Issue bpo-27229: Fix in-tree cross-build rule, by Xavier de Gaye
https://hg.python.org/cpython/rev/ffed402528c7

[python-dev]

New changeset ec214654708f by Martin Panter in branch '2.7':
Issue bpo-27229: Comment in middle of shell command fails on BSD and OS X
https://hg.python.org/cpython/rev/ec214654708f

New changeset de5b85f96266 by Martin Panter in branch '3.5':
Issue bpo-27229: Comment in middle of shell command fails on BSD and OS X
https://hg.python.org/cpython/rev/de5b85f96266

New changeset b7a4c076ba40 by Martin Panter in branch 'default':
Issue bpo-27229: Merge makefile fix from 3.5
https://hg.python.org/cpython/rev/b7a4c076ba40

[vadmium]

Thanks Alex & Xavier.