build: expose option to enable or disable precompiled std headers

They are enabled by default, and Meson will also prints whether or not
they're enabled at the bottom at the end of configuration.

Change-Id: I48db238510bf9e74340b86f243f4bbe360794281

10 files changed, 31 insertions, 13 deletions

diff --git a/meson.build b/meson.build
index b98b1fb15..7fd29bdf5 100644
--- a/meson.build
+++ b/meson.build
@@ -129,6 +129,20 @@ endif
 
 cxx = meson.get_compiler('cpp')
 
+
+# clangd breaks when GCC is using precompiled headers lmao
+# https://git.lix.systems/lix-project/lix/issues/374
+should_pch = get_option('enable-pch-std')
+summary('PCH C++ stdlib', should_pch, bool_yn : true)
+if should_pch
+  # Unlike basically everything else that takes a file, Meson requires the arguments to
+  # cpp_pch : to be strings and doesn't accept files(). So absolute path it is.
+  cpp_pch = [meson.project_source_root() / 'src/pch/precompiled-headers.hh']
+else
+  cpp_pch = []
+endif
+
+
 # Translate some historical and Mesony CPU names to Lixy CPU names.
 # FIXME(Qyriad): the 32-bit x86 code is not tested right now, because cross compilation for Lix
 # to those architectures is currently broken for other reasons, namely:
diff --git a/meson.options b/meson.options
index 6b13fa8a0..fc2050809 100644
--- a/meson.options
+++ b/meson.options
@@ -64,3 +64,7 @@ option('internal-api-docs', type : 'feature', value : 'auto',
 option('profile-dir', type : 'string', value : 'etc/profile.d',
   description : 'the path to install shell profile files',
 )
+
+option('enable-pch-std', type : 'boolean', value : true,
+  description : 'whether to use precompiled headers for C++\'s standard library (breaks clangd if you\'re using GCC)',
+)
diff --git a/src/libcmd/meson.build b/src/libcmd/meson.build
index 4dc0714c8..3d92f36a4 100644
--- a/src/libcmd/meson.build
+++ b/src/libcmd/meson.build
@@ -54,7 +54,7 @@ libcmd = library(
     nlohmann_json,
     lix_doc
   ],
-  cpp_pch : ['../pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
   install : true,
   # FIXME(Qyriad): is this right?
   install_rpath : libdir,
diff --git a/src/libexpr/meson.build b/src/libexpr/meson.build
index e60a85b5d..080fdb443 100644
--- a/src/libexpr/meson.build
+++ b/src/libexpr/meson.build
@@ -145,7 +145,7 @@ libexpr = library(
   include_directories : [
     '../libmain',
   ],
-  cpp_pch : ['../pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
   install : true,
   # FIXME(Qyriad): is this right?
   install_rpath : libdir,
diff --git a/src/libfetchers/meson.build b/src/libfetchers/meson.build
index ee38b6cda..b66d0b9f9 100644
--- a/src/libfetchers/meson.build
+++ b/src/libfetchers/meson.build
@@ -30,7 +30,7 @@ libfetchers = library(
     liblixutil,
     nlohmann_json,
   ],
-  cpp_pch : ['../pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
   install : true,
   # FIXME(Qyriad): is this right?
   install_rpath : libdir,
diff --git a/src/libmain/meson.build b/src/libmain/meson.build
index 075aa83b2..a7cce287c 100644
--- a/src/libmain/meson.build
+++ b/src/libmain/meson.build
@@ -20,7 +20,7 @@ libmain = library(
     liblixutil,
     liblixstore,
   ],
-  cpp_pch : ['../pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
   install : true,
   # FIXME(Qyriad): is this right?
   install_rpath : libdir,
diff --git a/src/libstore/meson.build b/src/libstore/meson.build
index 7a129d22c..fa363bd19 100644
--- a/src/libstore/meson.build
+++ b/src/libstore/meson.build
@@ -220,7 +220,7 @@ libstore = library(
     nlohmann_json,
   ],
   cpp_args : cpp_args,
-  cpp_pch : ['../pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
   install : true,
   # FIXME(Qyriad): is this right?
   install_rpath : libdir,
diff --git a/src/libutil/meson.build b/src/libutil/meson.build
index 8c3377e76..f6d14a11b 100644
--- a/src/libutil/meson.build
+++ b/src/libutil/meson.build
@@ -129,7 +129,7 @@ libutil = library(
     openssl,
     nlohmann_json,
   ],
-  cpp_pch : ['../pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
   implicit_include_directories : true,
   install : true,
 )
diff --git a/src/nix/meson.build b/src/nix/meson.build
index 8115a3d08..22f148fcb 100644
--- a/src/nix/meson.build
+++ b/src/nix/meson.build
@@ -89,7 +89,7 @@ nix = executable(
     boehm,
     nlohmann_json,
   ],
-  cpp_pch : ['../pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
   install : true,
   # FIXME(Qyriad): is this right?
   install_rpath : libdir,
diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 06aff4626..0d3f00ba5 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -68,7 +68,7 @@ libutil_tester = executable(
     liblixutil_test_support,
     nlohmann_json,
   ],
-  cpp_pch : ['../../src/pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
 )
 
 test(
@@ -103,7 +103,7 @@ libstore_test_support = library(
   include_directories : include_directories(
     'libstore-support',
   ),
-  cpp_pch : ['../../src/pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
 )
 liblixstore_test_support = declare_dependency(
   include_directories : include_directories('libstore-support'),
@@ -137,7 +137,7 @@ libstore_tester = executable(
     gtest,
     nlohmann_json,
   ],
-  cpp_pch : ['../../src/pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
 )
 
 test(
@@ -169,7 +169,7 @@ libexpr_test_support = library(
   include_directories : include_directories(
     'libexpr-support',
   ),
-  cpp_pch : ['../../src/pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
 )
 liblixexpr_test_support = declare_dependency(
   include_directories : include_directories('libexpr-support'),
@@ -203,7 +203,7 @@ libexpr_tester = executable(
     gtest,
     nlohmann_json,
   ],
-  cpp_pch : ['../../src/pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
 )
 
 test(
@@ -230,7 +230,7 @@ libcmd_tester = executable(
     gtest,
     boost,
   ],
-  cpp_pch : ['../../src/pch/precompiled-headers.hh'],
+  cpp_pch : cpp_pch,
 )
 
 test(