rucc_session/
runtime.rs

1//! The headers the compiler ships, and the directory they appear to live in.
2//!
3//! Design: `spec/04-driver-and-cli.md` section 4.4.
4//!
5//! A hosted C implementation is two halves. The library ships `<stdio.h>` and everything that
6//! declares a function you link against. The compiler ships the handful of headers whose
7//! contents are not the library's to know: `<stdarg.h>` is the target's calling convention,
8//! `<limits.h>` and `<float.h>` are the target's types, and `<stddef.h>` is the ABI. No
9//! library can write those, which is why every compiler carries its own copies and why a
10//! compiler that carries none cannot preprocess a program as ordinary as SQLite.
11//!
12//! They are in the binary rather than on disk. A compiler that has to find its own
13//! installation directory before it can preprocess a file is a compiler that stops working
14//! when it is copied somewhere else, and a single static binary that works from anywhere is
15//! worth more here than the ability to edit a header without rebuilding.
16//!
17//! Since they are not on disk they need a name, because the search path is a list of
18//! directories and a diagnostic has to be able to say where a header came from. That name is
19//! [`DIR`], and the angle brackets are the point: no directory a user can create is spelled
20//! that way, so nothing on the real file system can shadow these or be shadowed by them.
21
22use std::path::Path;
23
24use rucc_diag::SourceBytes;
25
26/// The directory the shipped headers appear to be in.
27///
28/// Not a path. It is a name that cannot be one, so that `#include <stdarg.h>` resolving to
29/// `<builtin>/stdarg.h` reads as what it is, and so that a real directory can never collide
30/// with it.
31pub const DIR: &str = "<builtin>";
32
33/// Every shipped header, in the order they are listed here, which is sorted by name.
34///
35/// The text is in the binary. `include_str!` rather than a build script because the set is
36/// small and fixed, and because a build script would put the headers behind a step that has
37/// to run before anything can be read.
38const HEADERS: &[(&str, &str)] = &[
39    ("arm_neon.h", include_str!("../runtime/include/arm_neon.h")),
40    ("avx512bwintrin.h", include_str!("../runtime/include/avx512bwintrin.h")),
41    ("avx512fintrin.h", include_str!("../runtime/include/avx512fintrin.h")),
42    ("avx512vlintrin.h", include_str!("../runtime/include/avx512vlintrin.h")),
43    ("avx512vpopcntdqintrin.h", include_str!("../runtime/include/avx512vpopcntdqintrin.h")),
44    ("cpuid.h", include_str!("../runtime/include/cpuid.h")),
45    ("emmintrin.h", include_str!("../runtime/include/emmintrin.h")),
46    ("float.h", include_str!("../runtime/include/float.h")),
47    ("immintrin.h", include_str!("../runtime/include/immintrin.h")),
48    ("iso646.h", include_str!("../runtime/include/iso646.h")),
49    ("limits.h", include_str!("../runtime/include/limits.h")),
50    ("mm_malloc.h", include_str!("../runtime/include/mm_malloc.h")),
51    ("mmintrin.h", include_str!("../runtime/include/mmintrin.h")),
52    ("nmmintrin.h", include_str!("../runtime/include/nmmintrin.h")),
53    ("popcntintrin.h", include_str!("../runtime/include/popcntintrin.h")),
54    ("smmintrin.h", include_str!("../runtime/include/smmintrin.h")),
55    ("stdalign.h", include_str!("../runtime/include/stdalign.h")),
56    ("stdarg.h", include_str!("../runtime/include/stdarg.h")),
57    ("stdatomic.h", include_str!("../runtime/include/stdatomic.h")),
58    ("stdbool.h", include_str!("../runtime/include/stdbool.h")),
59    ("stddef.h", include_str!("../runtime/include/stddef.h")),
60    ("stdint.h", include_str!("../runtime/include/stdint.h")),
61    ("stdnoreturn.h", include_str!("../runtime/include/stdnoreturn.h")),
62    ("vpclmulqdqintrin.h", include_str!("../runtime/include/vpclmulqdqintrin.h")),
63    ("x86intrin.h", include_str!("../runtime/include/x86intrin.h")),
64    ("xmmintrin.h", include_str!("../runtime/include/xmmintrin.h")),
65    ("xsaveintrin.h", include_str!("../runtime/include/xsaveintrin.h")),
66];
67
68/// The names of the shipped headers, sorted.
69#[must_use]
70pub fn names() -> Vec<&'static str> {
71    HEADERS.iter().map(|&(name, _)| name).collect()
72}
73
74/// The text of one shipped header, by its name alone.
75#[must_use]
76pub fn header(name: &str) -> Option<&'static str> {
77    HEADERS.iter().find(|&&(have, _)| have == name).map(|&(_, text)| text)
78}
79
80/// Reads a path that an include search produced, when it names a shipped header.
81///
82/// The path is [`DIR`] joined with the header's name, which on Windows means a backslash
83/// between them, so the two halves are compared rather than the string.
84#[must_use]
85pub fn read(path: &Path) -> Option<SourceBytes> {
86    if path.parent() != Some(Path::new(DIR)) {
87        return None;
88    }
89    let name = path.file_name()?.to_str()?;
90    header(name).map(SourceBytes::new)
91}
92
93#[cfg(test)]
94mod tests {
95    use std::path::PathBuf;
96
97    use super::*;
98
99    #[test]
100    fn the_shipped_headers_are_read_by_the_name_the_search_path_builds() {
101        let path = PathBuf::from(DIR).join("stdarg.h");
102        let bytes = read(&path).expect("stdarg.h is shipped");
103        let text = String::from_utf8(bytes.as_ref().to_vec()).expect("utf-8");
104        assert!(text.contains("__builtin_va_list"));
105    }
106
107    #[test]
108    fn nothing_outside_the_builtin_directory_is_answered() {
109        assert!(read(Path::new("/usr/include/stdarg.h")).is_none());
110        assert!(read(Path::new("stdarg.h")).is_none());
111        assert!(read(&PathBuf::from(DIR).join("stdio.h")).is_none());
112        assert!(read(&PathBuf::from(DIR).join("sys").join("stdarg.h")).is_none());
113    }
114
115    #[test]
116    fn the_list_is_sorted_so_that_a_new_header_has_one_place_to_go() {
117        let mut sorted = names();
118        sorted.sort_unstable();
119        assert_eq!(names(), sorted);
120    }
121
122    /// Every header has to be idempotent and has to name itself in its own guard, because a
123    /// program includes `<stddef.h>` forty times and a guard copied from a neighbour is the
124    /// way one of them silently stops working.
125    #[test]
126    fn every_header_guards_itself_under_its_own_name() {
127        for &(name, text) in HEADERS {
128            let guard = format!("__RUCC_{}", name.trim_end_matches(".h").to_uppercase());
129            assert!(text.contains(&guard), "{name} does not mention {guard}");
130        }
131    }
132}
rucc_session/runtime.rs

rucc_session/
runtime.rs
