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[hermes] Don't pass overly-long arguments to Charon #3044

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[hermes] Don't pass overly-long arguments to Charon #3044

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18 changes: 17 additions & 1 deletion tools/hermes/src/charon.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -38,7 +38,23 @@ pub fn run_charon(args: &Args, roots: &Roots, packages: &[HermesArtifact]) -> Re
// deterministic ordering for testing (not important in production).
let mut start_from = artifact.start_from.clone();
start_from.sort();
cmd.arg("--start-from").arg(start_from.join(","));

let start_from_str = start_from.join(",");
// OS command-line length limits (Windows is ~32k; Linux `ARG_MAX` is
// usually larger, but variable)
const ARG_CHAR_LIMIT: usize = 32_768;
Comment on lines +43 to +45
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@gemini-code-assist gemini-code-assist bot Feb 12, 2026

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medium

For better code organization and to signal that this constant is not dependent on the loop, consider defining ARG_CHAR_LIMIT and its explanatory comment outside the for loop, for example, at the function level. While const means no runtime cost, this improves readability and maintainability.

if start_from_str.len() > ARG_CHAR_LIMIT {
// FIXME: Pass the list of entry points to Charon via a file instead
// of the command line.
bail!(
"The list of Hermes entry points for package '{}' is too large ({} bytes). \n\
This exceeds safe OS command-line limits.",
Comment on lines +50 to +51
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@gemini-code-assist gemini-code-assist bot Feb 12, 2026

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medium

The indentation on this line will be included in the final error message string, which is likely not intended and will result in a large amount of whitespace at the beginning of the second line of the error message. Consider removing the leading spaces for cleaner output.

                "The list of Hermes entry points for package '{}' is too large ({} bytes). \nThis exceeds safe OS command-line limits.",

artifact.name.package_name,
start_from_str.len()
);
}

cmd.arg("--start-from").arg(start_from_str);

// Separator for the underlying cargo command
cmd.arg("--");
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1 change: 1 addition & 0 deletions tools/hermes/tests/fixtures/os_arg_limit_exceeded/expected_status.txt
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@@ -0,0 +1 @@
failure
1 change: 1 addition & 0 deletions tools/hermes/tests/fixtures/os_arg_limit_exceeded/expected_stderr.txt
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@@ -0,0 +1 @@
The list of Hermes entry points for package 'large_pkg' is too large
Empty file added tools/hermes/tests/fixtures/os_arg_limit_exceeded/hermes.toml
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Empty file.
6 changes: 6 additions & 0 deletions tools/hermes/tests/fixtures/os_arg_limit_exceeded/source/Cargo.toml
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@@ -0,0 +1,6 @@
[package]
name = "large_pkg"
version = "0.1.0"
edition = "2021"

[dependencies]
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