support large integer constants #490

devietti · 2020-03-10T03:14:48Z

I was using cbindgen for a project recently where I needed to export a const from Rust that was larger than i64, which would cause gcc to complain that warning: integer constant is so large that it is unsigned. This small patch includes a ULL suffix on the constant in the generated code to avoid this issue.

…e too big to fit in a signed 64-bit integer

emilio · 2020-03-11T11:21:05Z

src/bindgen/ir/constant.rs

@@ -163,7 +163,11 @@ impl Literal {
                        other_code => format!(r"L'\U{:08X}'", other_code),
                    })),
                    syn::Lit::Int(ref value) => {
-                        Ok(Literal::Expr(value.base10_digits().to_string()))
+                        if value.base10_parse::<i64>().is_err() {
+                            Ok(Literal::Expr(format!("{}ULL", value.base10_digits())))


Hmm, what if it is negative? Do we need just LL instead?

Good question - per the C/C++ spec (https://en.cppreference.com/w/cpp/language/integer_literal, the Notes section):

There are no negative integer literals. Expressions such as -1 apply the unary minus operator to the value represented by the literal, which may involve implicit type conversions.

So to export a constant that has the value of i64::min_value(), the ULL suffix is needed because the magnitude of the value is too large to fit into a signed 64-bit representation. I added this to the constant_big.rs test case.

Cool, that makes sense. Thanks for the extra test!

devietti · 2020-03-11T14:14:00Z

This also got me wondering about exporting i128/u128 constants, but those don't seem to be exported at the moment, perhaps because of issues like rust-lang/rust#54341.

emilio

Looks good to me, thanks!

emilio · 2020-03-11T14:33:56Z

src/bindgen/ir/constant.rs

@@ -163,7 +163,11 @@ impl Literal {
                        other_code => format!(r"L'\U{:08X}'", other_code),
                    })),
                    syn::Lit::Int(ref value) => {
-                        Ok(Literal::Expr(value.base10_digits().to_string()))
+                        if value.base10_parse::<i64>().is_err() {
+                            Ok(Literal::Expr(format!("{}ULL", value.base10_digits())))


Cool, that makes sense. Thanks for the extra test!

1276: Bump cbindgen from 0.13.1 to 0.13.2 r=tomtau a=dependabot-preview[bot] Bumps [cbindgen](https://github.com/eqrion/cbindgen) from 0.13.1 to 0.13.2. <details> <summary>Changelog</summary> <p><em>Sourced from <a href="https://github.com/eqrion/cbindgen/blob/master/CHANGES">cbindgen's changelog</a>.</em></p> <blockquote> <h2>0.13.2</h2> <pre><code> * Constants now have suitable documentation. ([#471](mozilla/cbindgen#471)) * Fixed some C warnings by emitting void when there are no arguments. ([#470](mozilla/cbindgen#470)) * Avoids reading cargo.toml when not needed, which can cause panics in workspace situations. * Only write `default` cases if the switch is not exhaustive. ([#475](mozilla/cbindgen#475)) * Some warnings have been refined. ([#477](mozilla/cbindgen#477)) * Code generation for static arrays has been fixed. ([#479](mozilla/cbindgen#479)) * Opt-in support for constexpr in constants. ([#481](mozilla/cbindgen#481)) * Fix C code generation and some warnings when extremely large constants are used. ([#490](mozilla/cbindgen#490)) * Proper escaping of enum variants and fields. ([#483](mozilla/cbindgen#483)) * Added support for RefCell (as an opaque type) and Cell. ([#489](mozilla/cbindgen#489)) </code></pre> </blockquote> </details> <details> <summary>Commits</summary> <ul> <li><a href="https://github.com/eqrion/cbindgen/commit/17d7aad7d07dce8aa665aedbc75c39953afe1600"><code>17d7aad</code></a> Release v0.13.2</li> <li><a href="https://github.com/eqrion/cbindgen/commit/fc577f2a28898b5345ed431fb172c4ede84fa2bf"><code>fc577f2</code></a> support large integer constants (<a href="https://github-redirect.dependabot.com/eqrion/cbindgen/issues/490">#490</a>)</li> <li><a href="https://github.com/eqrion/cbindgen/commit/6218281443ff9bb21c9502369497f7a7c24dd078"><code>6218281</code></a> updated constant_big test case with large negative numbers</li> <li><a href="https://github.com/eqrion/cbindgen/commit/8638652d1d72296888b540f1ae4a194991eba08b"><code>8638652</code></a> ran rustfmt</li> <li><a href="https://github.com/eqrion/cbindgen/commit/7101465403dec23f8752d4b6359e998e89ca3b6b"><code>7101465</code></a> avoid gcc warning by appending ULL suffix to integer literals that are too bi...</li> <li><a href="https://github.com/eqrion/cbindgen/commit/5a4d74b9118928946dd10a49c4891a2610c55437"><code>5a4d74b</code></a> ir: escape export_name while writing source of EnumVariant</li> <li><a href="https://github.com/eqrion/cbindgen/commit/e2b2c81221581f21e40d98045323c5d0b7844e0c"><code>e2b2c81</code></a> ir: escape tagged union's field name</li> <li><a href="https://github.com/eqrion/cbindgen/commit/c3442809b9e0be814918de6281469a955acfe7df"><code>c344280</code></a> tests: Add tests for cell and refcell.</li> <li><a href="https://github.com/eqrion/cbindgen/commit/249b41ce8a57db2c46fdd74b65f045cfc46ed4c0"><code>249b41c</code></a> ir: Add support for RefCell and Cell.</li> <li><a href="https://github.com/eqrion/cbindgen/commit/6654f99251769e9e037824d471f9f39e8d536b90"><code>6654f99</code></a> main: Provide a somewhat-useful error message for --verify changes.</li> <li>Additional commits viewable in <a href="https://github.com/eqrion/cbindgen/compare/v0.13.1...v0.13.2">compare view</a></li> </ul> </details> <br /> [![Dependabot compatibility score](https://api.dependabot.com/badges/compatibility_score?dependency-name=cbindgen&package-manager=cargo&previous-version=0.13.1&new-version=0.13.2)](https://dependabot.com/compatibility-score/?dependency-name=cbindgen&package-manager=cargo&previous-version=0.13.1&new-version=0.13.2) Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. 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Bump cbindgen from 0.9.1 to 0.14.1 Bumps [cbindgen](https://github.com/eqrion/cbindgen) from 0.9.1 to 0.14.1. <details> <summary>Changelog</summary> <p><em>Sourced from <a href="https://github.com/eqrion/cbindgen/blob/master/CHANGES">cbindgen's changelog</a>.</em></p> <blockquote> <h2>0.14.1</h2> <pre><code> * Handle mangling pointers. ([#508](mozilla/cbindgen#508)) * Unconditionally generate a return statement in partialeq implementations. ([#509](mozilla/cbindgen#509)) </code></pre> <h2>0.14.0</h2> <pre><code> * Minor tweak at how [export.exclude] is handled to allow excluding generic instantiations in C mode. ([#501](mozilla/cbindgen#501)) * Documented cpp_compat option. ([#496](mozilla/cbindgen#496)) * Fixed a panic when parsing associated constants for a built-in type. ([#494](mozilla/cbindgen#494)) </code></pre> <h2>0.13.2</h2> <pre><code> * Constants now have suitable documentation. ([#471](mozilla/cbindgen#471)) * Fixed some C warnings by emitting void when there are no arguments. ([#470](mozilla/cbindgen#470)) * Avoids reading cargo.toml when not needed, which can cause panics in workspace situations. * Only write `default` cases if the switch is not exhaustive. ([#475](mozilla/cbindgen#475)) * Some warnings have been refined. ([#477](mozilla/cbindgen#477)) * Code generation for static arrays has been fixed. ([#479](mozilla/cbindgen#479)) * Opt-in support for constexpr in constants. ([#481](mozilla/cbindgen#481)) * Fix C code generation and some warnings when extremely large constants are used. ([#490](mozilla/cbindgen#490)) * Proper escaping of enum variants and fields. ([#483](mozilla/cbindgen#483)) * Added support for RefCell (as an opaque type) and Cell. ([#489](mozilla/cbindgen#489)) </code></pre> <h2>0.13.1</h2> <pre><code> * Support `#[cfg]` on individual enum variants. ([#469](mozilla/cbindgen#469)) </code></pre> <h2>0.13.0</h2> <pre><code> * Support 'swift_name' attributes on generated functions ([#449](mozilla/cbindgen#449)) * Add [export.pre_body] to config ([#452](mozilla/cbindgen#452)) * Handle new line in doc attribute ([#454](mozilla/cbindgen#454)) * Add support for `Self` in tagged enums, structs and unions ([#455](mozilla/cbindgen#455), [#455](mozilla/cbindgen#455), [#456](mozilla/cbindgen#456)) * Make sentinel variant respect regular config ([#459](mozilla/cbindgen#459)) * Fix layout of tagged enums with size under some configurations ([#463](mozilla/cbindgen#463)) * Add an option to allow configuring the order of function names in generated headers ([#466](mozilla/cbindgen#466)) </code></pre> <h2>0.12.2</h2> <pre><code> * Fixed version detection with lockfile v2. mozilla/cbindgen#446 * Added support for export_name on functions. mozilla/cbindgen#447 </code></pre> <h2>0.12.1</h2> <pre><code> * Added support for #[repr*64)] on enums. mozilla/cbindgen#441 * Added support to generate plain enums instead of enum classes for C++. mozilla/cbindgen#443 * Fixed dependency resolution with lockfile v2. mozilla/cbindgen#438 </code></pre> </tr></table> ... 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devietti added 2 commits March 9, 2020 23:11

avoid gcc warning by appending ULL suffix to integer literals that ar…

7101465

…e too big to fit in a signed 64-bit integer

ran rustfmt

8638652

emilio reviewed Mar 11, 2020

View reviewed changes

updated constant_big test case with large negative numbers

6218281

emilio approved these changes Mar 11, 2020

View reviewed changes

emilio merged commit fc577f2 into mozilla:master Mar 11, 2020

emilio mentioned this pull request Jul 31, 2020

double negative for i64 min value with i64 suffix #553

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support large integer constants #490

support large integer constants #490

devietti commented Mar 10, 2020

emilio Mar 11, 2020

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emilio Mar 11, 2020

support large integer constants #490

support large integer constants #490

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