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posix: always seek to EOF when opening a file in append mode...
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.
Augie Fackler - - Load All Authors

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r43163:97ada9b8 5.0.2 stable
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test-fastannotate-corrupt.t
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/ tests / test-fastannotate-corrupt.t
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$ cat >> $HGRCPATH << EOF
> [extensions]
> fastannotate=
> EOF
$ hg init repo
$ cd repo
$ for i in 0 1 2 3 4; do
> echo $i >> a
> echo $i >> b
> hg commit -A -m $i a b
> done
use the "debugbuildannotatecache" command to build annotate cache at rev 0
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=0
fastannotate: a: 1 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
"debugbuildannotatecache" should work with broken cache (and other files would
be built without being affected). note: linelog being broken is only noticed
when we try to append to it.
$ echo 'CORRUPT!' >> .hg/fastannotate/default/a.m
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=1
fastannotate: a: rebuilding broken cache
fastannotate: a: 2 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
$ echo 'CANNOT REUSE!' > .hg/fastannotate/default/a.l
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=2
fastannotate: a: rebuilding broken cache
fastannotate: a: 3 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
$ rm .hg/fastannotate/default/a.m
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=3
fastannotate: a: rebuilding broken cache
fastannotate: a: 4 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
$ rm .hg/fastannotate/default/a.l
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=3
$ hg debugbuildannotatecache --debug --config fastannotate.mainbranch=4
fastannotate: a: rebuilding broken cache
fastannotate: a: 5 new changesets in the main branch
fastannotate: b: 1 new changesets in the main branch
"fastannotate" should deal with file corruption as well
$ rm -rf .hg/fastannotate
$ hg fastannotate --debug -r 0 a
fastannotate: a: 1 new changesets in the main branch
0: 0
$ echo 'CORRUPT!' >> .hg/fastannotate/default/a.m
$ hg fastannotate --debug -r 0 a
fastannotate: a: cache broken and deleted
fastannotate: a: 1 new changesets in the main branch
0: 0
$ echo 'CORRUPT!' > .hg/fastannotate/default/a.l
$ hg fastannotate --debug -r 1 a
fastannotate: a: cache broken and deleted
fastannotate: a: 2 new changesets in the main branch
0: 0
1: 1
$ rm .hg/fastannotate/default/a.l
$ hg fastannotate --debug -r 1 a
fastannotate: a: using fast path (resolved fctx: True)
fastannotate: a: cache broken and deleted
fastannotate: a: 2 new changesets in the main branch
0: 0
1: 1
$ rm .hg/fastannotate/default/a.m
$ hg fastannotate --debug -r 2 a
fastannotate: a: cache broken and deleted
fastannotate: a: 3 new changesets in the main branch
0: 0
1: 1
2: 2