Patch-Source: https://github.com/andrewchambers/bupstash/pull/381
--
From 9950cabff4d1a2714706622b88537f6572b8a1de Mon Sep 17 00:00:00 2001
From: Jakub Jirutka <jakub@jirutka.cz>
Date: Sat, 15 Apr 2023 00:21:14 +0200
Subject: [PATCH] Allow build with system-provided libsqlite (dynamically
 linked)

This is mainly for Linux distributions that package bupstash.
Linux distributions generally dislike bundled (statically linked)
dependencies, both for security reasons and to save users from wasting
network traffic and disk space by having dozens of copies of the same
library bundled in different binaries.

Notes:

The `modern_sqlite` feature of rusqlite is implicitly enabled by the
`bundled` feature, so it's not new here. This feature is needed because
it enables `libsqlite3-sys/bundled_bindings` which is needed for
`src/fstx2.rs` to build (it doesn't build with `buildtime_bindgen`, dunno
why).

sqlite has a very stable API and ABI, so it's not necessary to ensure
exact version matching. And it's undesirable when linking with
system-provided libsqlite, because it would require rebuilding bupstash
every time libsqlite is upgraded to a new patch version (e.g. with fixed
security bug). However, I kept the assert and disabled it just for
builds without bundled sqlite.
---
 Cargo.toml      |  4 +++-
 build.rs        | 16 ++++++++++------
 src/cksumvfs.rs |  5 +++++
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 48338062..d6faaf48 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,7 +15,9 @@ codegen-units = 1
 incremental = false
 
 [features]
+default = ["bundled-sqlite"]
 simd-rollsum = []
+bundled-sqlite = ["rusqlite/bundled"]
 
 [dependencies]
 
@@ -24,7 +26,7 @@ crossbeam-utils = "0.8"
 crossbeam-channel = "0.5"
 blake3 = "1"
 itertools = "0.10"
-rusqlite = { version = "0.25", features = ["bundled"] }
+rusqlite = { version = "0.25", features = ["modern_sqlite"] }
 lz4 = "1.2"
 zstd-safe = { version = "6.0", features = ["std", "experimental"] }
 anyhow = "1"
diff --git a/build.rs b/build.rs
index 9809ffb6..ffe8de76 100644
--- a/build.rs
+++ b/build.rs
@@ -2,11 +2,15 @@ fn main() {
     pkg_config::probe_library("libsodium").unwrap();
 
     println!("cargo:rerun-if-changed=csrc/cksumvfs/sqlite3.h");
-    cc::Build::new()
+
+    let mut build = cc::Build::new();
+    build
         .warnings(false) // Not our code/warnings to fix.
-        .flag("-DSQLITE_CKSUMVFS_STATIC")
-        .flag("-Icsrc/cksumvfs")
-        .file("csrc/cksumvfs/cksumvfs.c")
-        .file("csrc/cksumvfs/cksumvfs_sqlite_version_number.c")
-        .compile("cksumvfs");
+        .flag("-DSQLITE_CKSUMVFS_STATIC");
+    if cfg!(feature = "bundled-sqlite") {
+        build
+            .flag("-Icsrc/cksumvfs")
+            .file("csrc/cksumvfs/cksumvfs_sqlite_version_number.c");
+    }
+    build.file("csrc/cksumvfs/cksumvfs.c").compile("cksumvfs");
 }
diff --git a/src/cksumvfs.rs b/src/cksumvfs.rs
index f95524e5..e9cd5a43 100644
--- a/src/cksumvfs.rs
+++ b/src/cksumvfs.rs
@@ -3,13 +3,18 @@
 // For more info see: https://www.sqlite.org/cksumvfs.html
 
 extern "C" {
+    #[cfg(feature = "bundled-sqlite")]
     fn cksumvfs_sqlite_version_number() -> ::std::os::raw::c_int;
+
     fn sqlite3_register_cksumvfs(unused: *const u8) -> ::std::os::raw::c_int;
 }
 
 pub fn register_cksumvfs() {
     // Because have our own copy of the sqlite3 header file, this
     // test ensures we are using the same header rusqlite used.
+    // This is not needed (nor desirable) when building with a
+    // system-provided libsqlite.
+    #[cfg(feature = "bundled-sqlite")]
     assert_eq!(
         unsafe { cksumvfs_sqlite_version_number() },
         rusqlite::version_number()