Clean some header related things.

Revert most of "Hack together a fix for the public headers"

- The `libmain` change is kept, and one more libmain change is made.
  (Need to update Meson and Nix per the package alike).

- The S3 situation is fixed in a different way: the variable is public
  now, used in the header, and fixed accordingly.

- Fix TODO for `HAVE_EMBEDDED_SANDBOX_SHELL`

This reverts commit 2b51250534.

src/libexpr/expr-config.hh

@@ -1,3 +0,0 @@
-// TODO: Remove this damn file while keeping public config headers working
-#error \
-    "This file is a placeholder. It only exists so that meson accepts the symbolic link include/nix/expr/config.hh to this file, but we expect meson to overwrite it with the real file. Apparently that did not happen. I deeply apologize for this mess."

src/libexpr/include/nix/expr/config.hh

@@ -1 +0,0 @@
-../../../expr-config.hh

src/libexpr/include/nix/expr/meson.build

@@ -10,7 +10,6 @@ config_pub_h = configure_file(
 headers = [config_pub_h] + files(
   'attr-path.hh',
   'attr-set.hh',
-  'config.hh',
   'eval-cache.hh',
   'eval-error.hh',
   'eval-gc.hh',

src/libexpr/meson.build

@@ -79,11 +79,6 @@ config_priv_h = configure_file(
   output : 'expr-config-private.hh',
 )
 
-config_pub_h = configure_file(
-  configuration : configdata_pub,
-  output : 'expr-config.hh',
-)
-
 subdir('nix-meson-build-support/common')
 
 parser_tab = custom_target(
@@ -168,8 +163,6 @@ subdir('primops')
 subdir('nix-meson-build-support/export-all-symbols')
 subdir('nix-meson-build-support/windows-version')
 
-headers += [config_pub_h]
-
 this_library = library(
   'nixexpr',
   sources,
@@ -188,8 +181,4 @@ install_headers(headers, subdir : 'nix/expr', preserve_path : true)
 
 libraries_private = []
 
-nixexpr_dep = declare_dependency(
-  include_directories : include_directories('.'),
-  link_with : this_library,
-)
 subdir('nix-meson-build-support/export')

src/libmain/meson.build

@@ -17,12 +17,14 @@ subdir('nix-meson-build-support/deps-lists')
 configdata = configuration_data()
 
 deps_private_maybe_subproject = [
-  # This dependency may be very limited; was introduced for NIX_USE_BOEHMGC macro dependency
-  dependency('nix-expr'),
 ]
 deps_public_maybe_subproject = [
   dependency('nix-util'),
   dependency('nix-store'),
+  # FIXME: This is only here for the NIX_USE_BOEHMGC macro dependency
+  #        Removing nix-expr will make the build more concurrent and is
+  #        architecturally nice, perhaps.
+  dependency('nix-expr'),
 ]
 subdir('nix-meson-build-support/subprojects')
 

src/libstore-tests/meson.build

@@ -40,9 +40,6 @@ deps_private += gtest
 configdata = configuration_data()
 configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
 
-aws_s3 = dependency('aws-cpp-sdk-s3', required : false)
-configdata.set('ENABLE_S3', aws_s3.found().to_int())
-
 config_priv_h = configure_file(
   configuration : configdata,
   output : 'store-tests-config.hh',

src/libstore-tests/s3-binary-cache-store.cc

@@ -1,10 +1,9 @@
-#include "store-tests-config.hh"
-#if ENABLE_S3
+#include "nix/store/s3-binary-cache-store.hh"
+
+#if NIX_WITH_S3_SUPPORT
 
 #  include <gtest/gtest.h>
 
-#  include "nix/store/s3-binary-cache-store.hh"
-
 namespace nix {
 
 TEST(S3BinaryCacheStore, constructConfig)

src/libstore/filetransfer.cc

@@ -9,7 +9,7 @@
 #include "nix/util/signals.hh"
 
 #include "store-config-private.hh"
-#if ENABLE_S3
+#if NIX_WITH_S3_SUPPORT
 #include <aws/core/client/ClientConfiguration.h>
 #endif
 
@@ -756,7 +756,7 @@ struct curlFileTransfer : public FileTransfer
         #endif
     }
 
-#if ENABLE_S3
+#if NIX_WITH_S3_SUPPORT
     std::tuple<std::string, std::string, Store::Params> parseS3Uri(std::string uri)
     {
         auto [path, params] = splitUriAndParams(uri);
@@ -779,7 +779,7 @@ struct curlFileTransfer : public FileTransfer
         if (hasPrefix(request.uri, "s3://")) {
             // FIXME: do this on a worker thread
             try {
-#if ENABLE_S3
+#if NIX_WITH_S3_SUPPORT
                 auto [bucketName, key, params] = parseS3Uri(request.uri);
 
                 std::string profile = getOr(params, "profile", "");

src/libstore/include/nix/store/s3-binary-cache-store.hh

@@ -1,9 +1,13 @@
 #pragma once
 ///@file
 
-#include "nix/store/binary-cache-store.hh"
+#include "nix/store/config.hh"
 
-#include <atomic>
+#if NIX_WITH_S3_SUPPORT
+
+#  include "nix/store/binary-cache-store.hh"
+
+#  include <atomic>
 
 namespace nix {
 
@@ -125,3 +129,5 @@ public:
 };
 
 }
+
+#endif

src/libstore/include/nix/store/s3.hh

@@ -1,7 +1,7 @@
 #pragma once
 ///@file
 #include "store-config-private.hh"
-#if ENABLE_S3
+#if NIX_WITH_S3_SUPPORT
 
 #include "nix/util/ref.hh"
 

src/libstore/meson.build

@@ -126,7 +126,8 @@ deps_private += sqlite
 # AWS C++ SDK has bad pkg-config. See
 # https://github.com/aws/aws-sdk-cpp/issues/2673 for details.
 aws_s3 = dependency('aws-cpp-sdk-s3', required : false)
-configdata_priv.set('ENABLE_S3', aws_s3.found().to_int())
+# The S3 store definitions in the header will be hidden based on this variables.
+configdata_pub.set('NIX_WITH_S3_SUPPORT', aws_s3.found().to_int())
 if aws_s3.found()
   aws_s3 = declare_dependency(
     include_directories: include_directories(aws_s3.get_variable('includedir')),
@@ -153,13 +154,13 @@ endforeach
 
 busybox = find_program(get_option('sandbox-shell'), required : false)
 
+# This one goes in config.h
+# The path to busybox is passed as a -D flag when compiling this_library.
+# This solution is inherited from the old make buildsystem
+# TODO: do this differently?
+configdata_priv.set('HAVE_EMBEDDED_SANDBOX_SHELL', get_option('embedded-sandbox-shell').to_int())
+
 if get_option('embedded-sandbox-shell')
-  # This one goes in config.h
-  # The path to busybox is passed as a -D flag when compiling this_library.
-  # This solution is inherited from the old make buildsystem
-  # TODO: do this differently?
-  # TODO: at least define it unconditionally, so we get checking from -Wundef
-  configdata_priv.set('HAVE_EMBEDDED_SANDBOX_SHELL', 1)
   hexdump = find_program('hexdump', native : true)
   embedded_sandbox_shell_gen = custom_target(
     'embedded-sandbox-shell.gen.hh',
@@ -182,11 +183,6 @@ config_priv_h = configure_file(
   output : 'store-config-private.hh',
 )
 
-config_pub_h = configure_file(
-  configuration : configdata_pub,
-  output : 'store-config.hh',
-)
-
 subdir('nix-meson-build-support/common')
 
 sources = files(
@@ -369,7 +365,7 @@ this_library = library(
   install : true,
 )
 
-install_headers(headers + [ config_pub_h ], subdir : 'nix/store', preserve_path : true)
+install_headers(headers, subdir : 'nix/store', preserve_path : true)
 
 libraries_private = []
 

src/libstore/s3-binary-cache-store.cc

@@ -1,10 +1,10 @@
-#include "store-config-private.hh"
-#if ENABLE_S3
+#include "nix/store/s3-binary-cache-store.hh"
+
+#if NIX_WITH_S3_SUPPORT
 
 #include <assert.h>
 
 #include "nix/store/s3.hh"
-#include "nix/store/s3-binary-cache-store.hh"
 #include "nix/store/nar-info.hh"
 #include "nix/store/nar-info-disk-cache.hh"
 #include "nix/store/globals.hh"

src/libstore/unix/build/local-derivation-goal.cc

@@ -2017,7 +2017,7 @@ void LocalDerivationGoal::runChild()
             for (auto & i : pathsInChroot) {
                 if (i.second.source == "/proc") continue; // backwards compatibility
 
-                #ifdef HAVE_EMBEDDED_SANDBOX_SHELL
+                #if HAVE_EMBEDDED_SANDBOX_SHELL
                 if (i.second.source == "__embedded_sandbox_shell__") {
                     static unsigned char sh[] = {
                         #include "embedded-sandbox-shell.gen.hh"