Thread

1. MinGW ccache snafu on CI

   Thomas Munro <thomas.munro@gmail.com> — 2026-07-04T04:44:47Z

   Hi,
   
   As previously reported[1] (also discussed on Discord a few times), the
   MinGW CI job is capable of getting confused like this:
   
   Cache restored from key: ccache:windows-mingw:thread-work:28559723796:1
   
   # check for "D:/a/postgres/postgres/build/tmp_install/usr/local/pgsql/bin/vacuumdb"
   failed: incorrect version: found "vacuumdb (PostgreSQL) 19beta1",
   expected "vacuumdb (PostgreSQL) 20devel"
   
   Apparently ccache failed to recompile stuff that it should have, and
   produced a stale .o from an earlier build in the same repo/branch.
   While "19beta1" and "20devel" have the same length, I doubt that a
   mere few hundred monkeys with typewriters have found multiple hash
   collisions...
   
   One observation is that the MinGW job is using precompiled headers
   (-Db_pch=true).  I wonder if we might be using the wrong switches[2],
   but I don't claim to understand that stuff...
   
   So is the MSVC job, but I don't recall hearing of any problems there.
   
   [1] https://www.postgresql.org/message-id/flat/E1vOJwR-001XFf-0r%40gemulon.postgresql.org
   [2] https://ccache.dev/manual/4.1.html#_precompiled_headers
   
   
   
   

2. Re: MinGW ccache snafu on CI

   Andres Freund <andres@anarazel.de> — 2026-07-07T17:37:03Z

   Hi,
   
   On 2026-07-04 16:44:47 +1200, Thomas Munro wrote:
   > As previously reported[1] (also discussed on Discord a few times), the
   > MinGW CI job is capable of getting confused like this:
   > 
   > Cache restored from key: ccache:windows-mingw:thread-work:28559723796:1
   > 
   > # check for "D:/a/postgres/postgres/build/tmp_install/usr/local/pgsql/bin/vacuumdb"
   > failed: incorrect version: found "vacuumdb (PostgreSQL) 19beta1",
   > expected "vacuumdb (PostgreSQL) 20devel"
   > 
   > Apparently ccache failed to recompile stuff that it should have, and
   > produced a stale .o from an earlier build in the same repo/branch.
   > While "19beta1" and "20devel" have the same length, I doubt that a
   > mere few hundred monkeys with typewriters have found multiple hash
   > collisions...
   > 
   > One observation is that the MinGW job is using precompiled headers
   > (-Db_pch=true).  I wonder if we might be using the wrong switches[2],
   > but I don't claim to understand that stuff...
   > 
   > So is the MSVC job, but I don't recall hearing of any problems there.
   > 
   > [1] https://www.postgresql.org/message-id/flat/E1vOJwR-001XFf-0r%40gemulon.postgresql.org
   > [2] https://ccache.dev/manual/4.1.html#_precompiled_headers
   
   There's another thread about this:
   https://www.postgresql.org/message-id/CAN55FZ0tqR6Xz%3DiVFLc1BBoLOEHU775ARhcGYwggHA3XLA%3DoQg%40mail.gmail.com
   
   As suggested there, I think we need to add -fpch-deps for gcc, until either
   ccache is fixed or meson adds it automatically.
   
   Greetings,
   
   Andres Freund