Rollup merge of #109084 - dekrain:fix-panic-arg0-expansion, r=petroch…

…enkov

rustc driver: Remove argument 0 before at-expansion to prevent ICE

Under Unix-based operating systems, when I execute rustc by setting argv0 to ``@/dev/null`,` it will expand command-line arguments from this file, leading to an empty arglist, which then triggers an ICE by trying to remove first argument.

The panic message is this:
```
thread 'main' panicked at 'range start index 1 out of range for slice of length 0', compiler/rustc_driver/src/lib.rs:972:17
```

My fix is to remove the first argument before expanding arguments.

<details>
<summary>Full backtrace</summary>

```sh
% (exec -a `@/dev/null` `rustup which rustc`)
thread 'main' panicked at 'range start index 1 out of range for slice of length 0', compiler/rustc_driver/src/lib.rs:972:17
stack backtrace:
   0:     0x7fcec776659a - std::backtrace_rs::backtrace::libunwind::trace::h595f06c70adcc478
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7fcec776659a - std::backtrace_rs::backtrace::trace_unsynchronized::h177a0149c76cdde9
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fcec776659a - std::sys_common::backtrace::_print_fmt::hc0701fd2c3530c58
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7fcec776659a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hd4cd115d8750fd6c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7fcec77c839e - core::fmt::write::h93e2f5923c7eca08
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/fmt/mod.rs:1213:17
   5:     0x7fcec7756be5 - std::io::Write::write_fmt::h8162dbb45f0b9e62
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/io/mod.rs:1682:15
   6:     0x7fcec7766365 - std::sys_common::backtrace::_print::h1835ef8a8f9066da
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7fcec7766365 - std::sys_common::backtrace::print::hcb5e6388b9235f41
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7fcec776912f - std::panicking::default_hook::{{closure}}::h9c084969ccf9a722
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:267:22
   9:     0x7fcec7768e6b - std::panicking::default_hook::h68fa2ba3c3c6c12f
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:286:9
  10:     0x7fcecaab56e4 - <rustc_driver[f4ad927b3c57833d]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[d16e85342ea223d9]::ops::function::FnOnce<(&core[d16e85342ea223d9]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
  11:     0x7fcec776996a - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h4e6ced11e07d8b24
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/alloc/src/boxed.rs:2002:9
  12:     0x7fcec776996a - std::panicking::rust_panic_with_hook::h8d5c434518ef298c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:692:13
  13:     0x7fcec77696e9 - std::panicking::begin_panic_handler::{{closure}}::hf33414f5dabf6faf
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:579:13
  14:     0x7fcec7766a4c - std::sys_common::backtrace::__rust_end_short_backtrace::hc50389427413bb75
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/sys_common/backtrace.rs:137:18
  15:     0x7fcec77693f2 - rust_begin_unwind
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:575:5
  16:     0x7fcec77c4d43 - core::panicking::panic_fmt::h2de7a7938f816de8
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/panicking.rs:64:14
  17:     0x7fcec77cb492 - core::slice::index::slice_start_index_len_fail_rt::h0c87d85ce11d10f6
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/slice/index.rs:53:5
  18:     0x7fcec77cb416 - core::slice::index::slice_start_index_len_fail::h504609f2a6b168d1
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/slice/index.rs:41:9
  19:     0x7fceca0eca1f - rustc_driver[f4ad927b3c57833d]::handle_options
  20:     0x7fceca0e037f - <rustc_driver[f4ad927b3c57833d]::RunCompiler>::run
  21:     0x7fceca0dfd0d - <core[d16e85342ea223d9]::panic::unwind_safe::AssertUnwindSafe<rustc_driver[f4ad927b3c57833d]::main::{closure#0}> as core[d16e85342ea223d9]::ops::function::FnOnce<()>>::call_once
  22:     0x7fceca17ce89 - rustc_driver[f4ad927b3c57833d]::main
  23:     0x564f5f008a87 - rustc_main[f164605d1302e295]::main
  24:     0x564f5f008973 - std[3da461b304582a2c]::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>
  25:     0x564f5f008969 - <std[3da461b304582a2c]::rt::lang_start<()>::{closure#0} as core[d16e85342ea223d9]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  26:     0x7fcec774795c - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h699977d052768608
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/core/src/ops/function.rs:287:13
  27:     0x7fcec774795c - std::panicking::try::do_call::h4e121e623c70f903
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:483:40
  28:     0x7fcec774795c - std::panicking::try::hf9d919e062bc178a
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:447:19
  29:     0x7fcec774795c - std::panic::catch_unwind::h7a7b12272684cb97
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panic.rs:140:14
  30:     0x7fcec774795c - std::rt::lang_start_internal::{{closure}}::hd96b0eb4844b8762
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/rt.rs:148:48
  31:     0x7fcec774795c - std::panicking::try::do_call::h1af1f88f4f92a22c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:483:40
  32:     0x7fcec774795c - std::panicking::try::hf20d7abea7f0f097
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panicking.rs:447:19
  33:     0x7fcec774795c - std::panic::catch_unwind::hb0e084c3a9c042e4
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/panic.rs:140:14
  34:     0x7fcec774795c - std::rt::lang_start_internal::hca9d5c7277f5b67c
                               at /rustc/2c8cc343237b8f7d5a3c3703e3a87f2eb2c54a74/library/std/src/rt.rs:148:20
  35:     0x564f5f008ab7 - main
  36:     0x7fcec74a1790 - <unknown>
  37:     0x7fcec74a184a - __libc_start_main
  38:     0x564f5f00899e - <unknown>
  39:                0x0 - <unknown>

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.68.0 (2c8cc34 2023-03-06) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack
```
</details>

I also checked if I can trigger a similar problem by passing empty argument list to `execve`, but at least under Linux, it seems to always insert an empty first argument if there are none.

compiler/rustc_driver_impl/src/args.rs

@@ -18,6 +18,9 @@ fn arg_expand(arg: String) -> Result<Vec<String>, Error> {
     }
 }
 
+/// **Note:** This function doesn't interpret argument 0 in any special way.
+/// If this function is intended to be used with command line arguments,
+/// `argv[0]` must be removed prior to calling it manually.
 pub fn arg_expand_all(at_args: &[String]) -> Vec<String> {
     let mut args = Vec::new();
     for arg in at_args {

compiler/rustc_driver_impl/src/lib.rs

@@ -250,6 +250,16 @@ fn run_compiler(
         Box<dyn FnOnce(&config::Options) -> Box<dyn CodegenBackend> + Send>,
     >,
 ) -> interface::Result<()> {
+    // Throw away the first argument, the name of the binary.
+    // In case of at_args being empty, as might be the case by
+    // passing empty argument array to execve under some platforms,
+    // just use an empty slice.
+    //
+    // This situation was possible before due to arg_expand_all being
+    // called before removing the argument, enabling a crash by calling
+    // the compiler with @empty_file as argv[0] and no more arguments.
+    let at_args = at_args.get(1..).unwrap_or_default();
+
     let args = args::arg_expand_all(at_args);
 
     let Some(matches) = handle_options(&args) else { return Ok(()) };
@@ -1074,9 +1084,6 @@ fn print_flag_list<T>(
 /// So with all that in mind, the comments below have some more detail about the
 /// contortions done here to get things to work out correctly.
 pub fn handle_options(args: &[String]) -> Option<getopts::Matches> {
-    // Throw away the first argument, the name of the binary
-    let args = &args[1..];
-
     if args.is_empty() {
         // user did not write `-v` nor `-Z unstable-options`, so do not
         // include that extra information.

src/librustdoc/config.rs

@@ -314,7 +314,6 @@ impl Options {
         matches: &getopts::Matches,
         args: Vec<String>,
     ) -> Result<(Options, RenderOptions), i32> {
-        let args = &args[1..];
         // Check for unstable options.
         nightly_options::check_nightly_options(matches, &opts());
 

src/librustdoc/lib.rs

@@ -712,13 +712,23 @@ fn run_renderer<'tcx, T: formats::FormatRenderer<'tcx>>(
 }
 
 fn main_args(at_args: &[String]) -> MainResult {
+    // Throw away the first argument, the name of the binary.
+    // In case of at_args being empty, as might be the case by
+    // passing empty argument array to execve under some platforms,
+    // just use an empty slice.
+    //
+    // This situation was possible before due to arg_expand_all being
+    // called before removing the argument, enabling a crash by calling
+    // the compiler with @empty_file as argv[0] and no more arguments.
+    let at_args = at_args.get(1..).unwrap_or_default();
+
     let args = rustc_driver::args::arg_expand_all(at_args);
 
     let mut options = getopts::Options::new();
     for option in opts() {
         (option.apply)(&mut options);
     }
-    let matches = match options.parse(&args[1..]) {
+    let matches = match options.parse(&args) {
         Ok(m) => m,
         Err(err) => {
             early_error(ErrorOutputType::default(), err.to_string());