posix: always seek to EOF when opening a file in append mode Python 3 already does this, so skip it there. Consider the program: #include <stdio.h> int main() { FILE *f = fopen("narf", "w"); fprintf(f, "narf\n"); fclose(f); f = fopen("narf", "a"); printf("%ld\n", ftell(f)); fprintf(f, "troz\n"); printf("%ld\n", ftell(f)); return 0; } on macOS, FreeBSD, and Linux with glibc, this program prints 5 10 but on musl libc (Alpine Linux and probably others) this prints 0 10 By my reading of https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html this is technically correct, specifically: > Opening a file with append mode (a as the first character in the > mode argument) shall cause all subsequent writes to the file to be > forced to the then current end-of-file, regardless of intervening > calls to fseek(). in other words, the file position doesn't really matter in append-mode files, and we can't depend on it being at all meaningful unless we perform a seek() before tell() after open(..., 'a'). Experimentally after a .write() we can do a .tell() and it'll always be reasonable, but I'm unclear from reading the specification if that's a smart thing to rely on. This matches what we do on Windows and what Python 3 does for free, so let's just be consistent. Thanks to Yuya for the idea.

     1

  $ . $TESTDIR/wireprotohelpers.sh

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  $ hg init server

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  $ enablehttpv2 server

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  $ cd server

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  $ hg debugdrawdag << EOF

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  > H I J

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  > | | |

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  > E F G

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  > | |/

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  > C D

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  > |/

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  > B

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  > |

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  > A

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  > EOF

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  $ hg phase --force --secret J

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  $ hg phase --public E

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  $ hg log -r 'E + H + I + G + J' -T '{rev}:{node} {desc} {phase}\n'

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  4:78d2dca436b2f5b188ac267e29b81e07266d38fc E public

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  7:ae492e36b0c8339ffaf328d00b85b4525de1165e H draft

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  8:1d6f6b91d44aaba6d5e580bc30a9948530dbe00b I draft

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  6:29446d2dc5419c5f97447a8bc062e4cc328bf241 G draft

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  9:dec04b246d7cbb670c6689806c05ad17c835284e J secret

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  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log

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  $ cat hg.pid > $DAEMON_PIDS

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All non-secret heads returned by default

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  $ sendhttpv2peer << EOF

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  > command heads

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  > EOF

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  creating http peer for wire protocol version 2

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  sending heads command

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  response: [

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    b'\x1dok\x91\xd4J\xab\xa6\xd5\xe5\x80\xbc0\xa9\x94\x850\xdb\xe0\x0b',

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    b'\xaeI.6\xb0\xc83\x9f\xfa\xf3(\xd0\x0b\x85\xb4R]\xe1\x16^',

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    b')Dm-\xc5A\x9c_\x97Dz\x8b\xc0b\xe4\xcc2\x8b\xf2A'

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  ]

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    44

Requesting just the public heads works

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  $ sendhttpv2peer << EOF

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  > command heads

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  >     publiconly 1

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  > EOF

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  creating http peer for wire protocol version 2

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  sending heads command

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  response: [

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    b'x\xd2\xdc\xa46\xb2\xf5\xb1\x88\xac&~)\xb8\x1e\x07&m8\xfc'

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  ]

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  $ cat error.log