Files
neon/libs/postgres_ffi
sharnoff 9c35a09452 Improve build errors when postgres_ffi fails (#2460)
This commit does two things of note:

 1. Bumps the bindgen dependency from `0.59.1` to `0.60.1`. This gets us
    an actual error type from bindgen, so we can display what's wrong.
 2. Adds `anyhow` as a build dependency, so our error message can be
    prettier. It's already used heavily elsewhere in the crates in this
    repo, so I figured the fact it's a build dependency doesn't matter
    much.

I ran into this from running `cargo <cmd>` without running `make` first.
Here's a comparison of the compiler output in those two cases.

Before this commit:

```
error: failed to run custom build command for `postgres_ffi v0.1.0 ($repo_path/libs/postgres_ffi)`

Caused by:
  process didn't exit successfully: `$repo_path/target/debug/build/postgres_ffi-2f7253b3ad3ca840/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-changed=bindgen_deps.h

  --- stderr
  bindgen_deps.h:7:10: fatal error: 'c.h' file not found
  bindgen_deps.h:7:10: fatal error: 'c.h' file not found, err: true
  thread 'main' panicked at 'Unable to generate bindings: ()', libs/postgres_ffi/build.rs:135:14
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

After this commit:

```
error: failed to run custom build command for `postgres_ffi v0.1.0 ($repo_path/libs/postgres_ffi)`

Caused by:
  process didn't exit successfully: `$repo_path/target/debug/build/postgres_ffi-e01fb59602596748/build-script-build` (exit status: 1)
  --- stdout
  cargo:rerun-if-changed=bindgen_deps.h

  --- stderr
  bindgen_deps.h:7:10: fatal error: 'c.h' file not found
  Error: Unable to generate bindings

  Caused by:
      clang diagnosed error: bindgen_deps.h:7:10: fatal error: 'c.h' file not found
```
2022-09-16 08:37:44 -07:00
..

This module contains utilities for working with PostgreSQL file formats. It's a collection of structs that are auto-generated from the PostgreSQL header files using bindgen, and Rust functions to read and manipulate them.

There are also a bunch of constants in pg_constants.rs that are copied from various PostgreSQL headers, rather than auto-generated. They mostly should be auto-generated too, but that's a TODO.

The PostgreSQL on-disk file format is not portable across different CPU architectures and operating systems. It is also subject to change in each major PostgreSQL version. Currently, this module supports PostgreSQL v14 and v15: bindings and code that depends on them are version-specific. This code is organized in modules: postgres_ffi::v14 and postgres_ffi::v15 Version independend code is explicitly exported into shared postgres_ffi.

TODO: Currently, there is also some code that deals with WAL records in pageserver/src/waldecoder.rs. That should be moved into this module. The rest of the codebase should not have intimate knowledge of PostgreSQL file formats or WAL layout, that knowledge should be encapsulated in this module.