From 77df912a3172bbd3ea672708469d02ca938f79ee Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Wed, 15 Jul 2026 15:27:16 -0400 Subject: [PATCH v2] meson: Fix ccache issues when using precompiled headers with gcc Unfortunately the combination of gcc, precompiled headers, ccache and meson currently is not safe without further options. The dependencies emitted by gcc are insufficient to trigger rebuilds when headers "below" the precompiled headers are changed. Whether that's a ccache, gcc or meson bug is debatable. Luckily gcc's -fpch-deps option fixes the issue. This problem occasionally leads to build failures, e.g. if only c.h, postgres.h or pg_config_manual.h change. That's e.g. the case when creating a new major version branch. Discussion: https://postgr.es/m/CAN55FZ0tqR6Xz%3DiVFLc1BBoLOEHU775ARhcGYwggHA3XLA%3DoQg%40mail.gmail.com Discussion: https://postgr.es/m/CA+hUKG+s7Yvt0PUnSQUEjCjysV-7-51n9B1h468Le3VJi0x4ZQ@mail.gmail.com Discussion: https://postgr.es/m/phsrssp75npoyalqsolcd7fmnmlbzbmquc2p7w7mqjlw7432jk@bzskz3luyjvb Discussion: https://github.com/ccache/ccache/issues/1686 Backpatch-through: 16, where meson support was added --- meson.build | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/meson.build b/meson.build index 61b5681851e..f4cde249242 100644 --- a/meson.build +++ b/meson.build @@ -2185,6 +2185,12 @@ common_functional_flags = [ # Disable optimizations that assume no overflow; needed for gcc 4.3+ '-fwrapv', '-fexcess-precision=standard', + # Without -fpch-deps gcc emits dependencies that are insufficient for ccache + # to trigger a rebuild when the precompiled header changes. We could make + # this depend on using gcc and precompiled headers being enabled, but that's + # probably not worth it. See also + # https://github.com/ccache/ccache/issues/1686 + '-fpch-deps', ] cflags += cc.get_supported_arguments(common_functional_flags) -- 2.54.0.450.g9ac3f193c0