`argv[0]` is not accessible to Lean

Prerequisites

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• Reduce the issue to a minimal, self-contained, reproducible test case.
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Description

The lean def main is passed arg[1] to argv[argc - 1].

This is consistent with the behavior of Haskell's getArgs, but Lean does not provide haskell's getProgName.

IO.appPath is not a substitute for argv[0], as:

• argv[0] contains the pre-resolved symlinks
• The caller of exec can override argv[0] arbitrarily.

Context

Zulip thread

Steps to Reproduce

1. Create a lean binary foo
2. Run (exec -a secret_name ./lake/build/bin/foo)

Expected behavior: secret_name should either be in the first entry of args, or accessible via some IO API

Actual behavior: secret_name is lost forever:

https://github.com/leanprover/lean4/blob/01d414ac36dc28f3e424dabd36d818873fea655c/src/Lean/Compiler/IR/EmitC.lean#L173-L182

Versions

[Output of #eval Lean.versionString]
[OS version, if not using live.lean-lang.org.]

Additional Information

[Additional information, configuration or data that might be necessary to reproduce the issue]

Impact

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Start with the linked EmitC.lean lines 173–182 and reproduce the issue by building the foo binary and running exec -a secret_name ./lake/build/bin/foo. Trace how the command-line arguments reach Lean’s main; done means the caller-supplied argv[0] is preserved in the first argument or exposed through an IO API.