portable server with embedded for musl has different feature

packaging/musl/README.md

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+# Portable Linux server build
+
+This build produces one `x86_64` Linux server executable with embedded
+PostgreSQL. The Rust program is statically linked against musl. PostgreSQL is
+compiled against musl without optional host-library dependencies and is stored
+inside the executable by `postgresql_embedded`.
+
+PostgreSQL itself remains dynamically loadable so the `btree_gist` extension
+used by the migrations works. Its musl loader is included in the embedded
+archive, and static launcher executables invoke every PostgreSQL tool through
+that loader. Neither glibc, musl, PostgreSQL nor timezone data needs to be
+installed on the target machine.
+
+Build directly through the repository's Nix flake:
+
+```sh
+nix build '.?submodules=1#portable-server'
+```
+
+The `submodules=1` flag includes the workspace's nested Rust repositories. The
+artifact is available as `result/bin/server`. The derivation initializes a
+temporary cluster, creates `btree_gist`, sets the timezone to `UTC`, and checks
+that the final Rust executable has no ELF interpreter.
+
+The resulting executable is intended for 64-bit Linux kernels. Run it normally:
+
+```sh
+./result/bin/server server
+```
+
+Use the external PostgreSQL build on NixOS when preferred:
+
+```sh
+cargo build --release --package server --no-default-features
+```

packaging/musl/default.nix

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+{ pkgs, source, version }:
+
+let
+  muslPkgs = pkgs.pkgsMusl;
+  postgresqlVersion = "17.10";
+  postgresqlArchiveVersion = "17.10.0";
+  archiveName = "postgresql-${postgresqlArchiveVersion}-x86_64-unknown-linux-musl.tar.gz";
+
+  bootstrapInput = pname: inputs:
+    pkgs.lib.findFirst
+      (input: (input.pname or "") == pname)
+      (throw "Nixpkgs does not expose ${pname} for the musl toolchain")
+      inputs;
+  bootstrapRustPlatform = muslPkgs.makeRustPlatform {
+    rustc = bootstrapInput
+      "rustc-bootstrap"
+      muslPkgs.rustc-unwrapped.nativeBuildInputs;
+    cargo = bootstrapInput
+      "cargo-bootstrap"
+      muslPkgs.cargo.nativeBuildInputs;
+  };
+
+  staticOpenSSL = muslPkgs.openssl.overrideAttrs (old: {
+    configureFlags =
+      builtins.filter (flag: flag != "shared") old.configureFlags
+      ++ [ "no-shared" ];
+    doCheck = false;
+  });
+
+  postgresqlSource = pkgs.fetchurl {
+    url = "https://ftp.postgresql.org/pub/source/v${postgresqlVersion}/postgresql-${postgresqlVersion}.tar.bz2";
+    hash = "sha256-B4oDUW3NvbcF/sr0Feo9E6lWxYnkbwn+1ooG+wBZjJA=";
+  };
+
+  postgresqlArchive = muslPkgs.stdenv.mkDerivation {
+    pname = "komp-ac-postgresql-musl";
+    version = postgresqlArchiveVersion;
+    src = postgresqlSource;
+
+    nativeBuildInputs = [
+      pkgs.bison
+      pkgs.file
+      pkgs.flex
+      pkgs.gnutar
+      pkgs.gzip
+      pkgs.perl
+    ];
+
+    configurePhase = ''
+      runHook preConfigure
+      ./configure \
+        --prefix="$out/postgresql" \
+        --disable-nls \
+        --without-gssapi \
+        --without-icu \
+        --without-ldap \
+        --without-libxml \
+        --without-libxslt \
+        --without-llvm \
+        --without-lz4 \
+        --without-openssl \
+        --without-pam \
+        --without-readline \
+        --without-systemd \
+        --without-zlib \
+        --without-zstd
+      runHook postConfigure
+    '';
+
+    buildPhase = ''
+      runHook preBuild
+      make -j"$NIX_BUILD_CORES"
+      make -C contrib/btree_gist -j"$NIX_BUILD_CORES"
+      runHook postBuild
+    '';
+
+    installPhase = ''
+      runHook preInstall
+      make install-strip
+      make -C contrib/btree_gist install
+
+      "$CC" -static -Os -s -Wall -Wextra -Werror \
+        -o postgresql-launcher \
+        ${./postgresql-launcher.c}
+
+      mkdir -p "$out/postgresql/libexec"
+      for tool in "$out"/postgresql/bin/*; do
+        toolName="''${tool##*/}"
+        mv "$tool" "$out/postgresql/libexec/$toolName"
+        cp postgresql-launcher "$out/postgresql/bin/$toolName"
+      done
+      cp ${muslPkgs.musl}/lib/ld-musl-x86_64.so.1 \
+        "$out/postgresql/lib/ld-musl-x86_64.so.1"
+
+      file "$out/postgresql/bin/postgres" | grep -q 'statically linked'
+      "$out/postgresql/bin/postgres" --version
+
+      mkdir postgresql-data postgresql-socket
+      "$out/postgresql/bin/initdb" \
+        --auth=trust \
+        --no-locale \
+        -D "$PWD/postgresql-data"
+      "$out/postgresql/bin/pg_ctl" \
+        -D "$PWD/postgresql-data" \
+        -l "$PWD/postgresql.log" \
+        -o "-k $PWD/postgresql-socket -p 55432" \
+        -w start
+      "$out/postgresql/bin/psql" \
+        -h "$PWD/postgresql-socket" \
+        -p 55432 \
+        -d postgres \
+        -c "CREATE EXTENSION btree_gist; SET TIME ZONE 'UTC';"
+      "$out/postgresql/bin/pg_ctl" \
+        -D "$PWD/postgresql-data" \
+        -m fast \
+        -w stop
+
+      tar -C "$out" -czf "$out/${archiveName}" postgresql
+      runHook postInstall
+    '';
+
+    dontPatchELF = true;
+    dontStrip = true;
+  };
+in
+bootstrapRustPlatform.buildRustPackage {
+  pname = "komp-ac-server-portable";
+  inherit version source;
+  src = source;
+
+  cargoLock.lockFile = ../../Cargo.lock;
+  cargoBuildFlags = [
+    "--package"
+    "server"
+    "--no-default-features"
+    "--features"
+    "portable-postgres"
+  ];
+  auditable = false;
+  doCheck = false;
+
+  nativeBuildInputs = [
+    pkgs.binutils
+    pkgs.cmake
+    pkgs.file
+    pkgs.pkg-config
+    pkgs.protobuf
+  ];
+  buildInputs = [ staticOpenSSL ];
+
+  OPENSSL_STATIC = "1";
+  OPENSSL_LIB_DIR = "${staticOpenSSL.out}/lib";
+  OPENSSL_INCLUDE_DIR = "${staticOpenSSL.dev}/include";
+  POSTGRESQL_VERSION = "=${postgresqlArchiveVersion}";
+  KOMP_AC_POSTGRESQL_ARCHIVE = "${postgresqlArchive}/${archiveName}";
+  KOMP_AC_POSTGRESQL_VERSION = postgresqlArchiveVersion;
+  SQLX_OFFLINE = "true";
+  RUSTFLAGS = "-Ctarget-feature=+crt-static";
+
+  postInstall = ''
+    file "$out/bin/server" | grep -q 'statically linked'
+    ! readelf -l "$out/bin/server" | grep -q 'Requesting program interpreter'
+  '';
+
+  meta = {
+    description = "Portable komp_ac server with embedded musl PostgreSQL";
+    license = pkgs.lib.licenses.agpl3Plus;
+    platforms = [ "x86_64-linux" ];
+    mainProgram = "server";
+  };
+}

packaging/musl/postgresql-launcher.c

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+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static void fail(const char *message)
+{
+    fprintf(stderr, "embedded PostgreSQL launcher: %s\n", message);
+    exit(127);
+}
+
+static void join_path(char *destination, size_t capacity, const char *left, const char *right)
+{
+    int length = snprintf(destination, capacity, "%s/%s", left, right);
+    if (length < 0 || (size_t) length >= capacity)
+        fail("installation path is too long");
+}
+
+int main(int argc, char **argv)
+{
+    char executable[PATH_MAX];
+    ssize_t executable_length = readlink("/proc/self/exe", executable, sizeof(executable) - 1);
+    if (executable_length < 0) {
+        perror("embedded PostgreSQL launcher: /proc/self/exe");
+        return 127;
+    }
+    executable[executable_length] = '\0';
+
+    char *tool = strrchr(executable, '/');
+    if (tool == NULL || tool[1] == '\0')
+        fail("cannot determine the requested PostgreSQL tool");
+    tool++;
+
+    char root[PATH_MAX];
+    if ((size_t) executable_length >= sizeof(root))
+        fail("installation path is too long");
+    memcpy(root, executable, (size_t) executable_length + 1);
+
+    char *bin_separator = strrchr(root, '/');
+    if (bin_separator == NULL)
+        fail("cannot determine the PostgreSQL installation directory");
+    *bin_separator = '\0';
+    char *root_separator = strrchr(root, '/');
+    if (root_separator == NULL)
+        fail("cannot determine the PostgreSQL installation directory");
+    *root_separator = '\0';
+
+    char loader[PATH_MAX];
+    char library_path[PATH_MAX];
+    char real_tool[PATH_MAX];
+    join_path(loader, sizeof(loader), root, "lib/ld-musl-x86_64.so.1");
+    join_path(library_path, sizeof(library_path), root, "lib");
+
+    char real_tool_relative[PATH_MAX];
+    int relative_length = snprintf(
+        real_tool_relative,
+        sizeof(real_tool_relative),
+        "libexec/%s",
+        tool
+    );
+    if (relative_length < 0 || (size_t) relative_length >= sizeof(real_tool_relative))
+        fail("tool path is too long");
+    join_path(real_tool, sizeof(real_tool), root, real_tool_relative);
+
+    char **loader_argv = calloc((size_t) argc + 6, sizeof(char *));
+    if (loader_argv == NULL) {
+        perror("embedded PostgreSQL launcher: calloc");
+        return 127;
+    }
+
+    loader_argv[0] = loader;
+    loader_argv[1] = "--library-path";
+    loader_argv[2] = library_path;
+    loader_argv[3] = "--argv0";
+    loader_argv[4] = executable;
+    loader_argv[5] = real_tool;
+    for (int index = 1; index < argc; index++)
+        loader_argv[index + 5] = argv[index];
+
+    execv(loader, loader_argv);
+    fprintf(
+        stderr,
+        "embedded PostgreSQL launcher: cannot execute %s: %s\n",
+        real_tool,
+        strerror(errno)
+    );
+    return 127;
+}