embed-source: explicitly require -Zdwarf-version=5

Author: Mrmaxmeier

compiler/rustc_session/messages.ftl

@@ -14,6 +14,8 @@ session_crate_name_empty = crate name must not be empty
 
 session_crate_name_invalid = crate names cannot start with a `-`, but `{$s}` has a leading hyphen
 
+session_embed_source_insufficient_dwarf_version = `-Cembed-source=y` requires at least `-Z dwarf-version=5` while sesssion uses version {$dwarf_version}
+
 session_expr_parentheses_needed = parentheses are required to parse this as an expression
 
 session_failed_to_create_profiler = failed to create profiler: {$err}

compiler/rustc_session/src/errors.rs

@@ -163,6 +163,12 @@ pub(crate) struct UnsupportedDwarfVersion {
     pub(crate) dwarf_version: u32,
 }
 
+#[derive(Diagnostic)]
+#[diag(session_embed_source_insufficient_dwarf_version)]
+pub(crate) struct EmbedSourceInsufficientDwarfVersion {
+    pub(crate) dwarf_version: u32,
+}
+
 #[derive(Diagnostic)]
 #[diag(session_target_stack_protector_not_supported)]
 pub(crate) struct StackProtectorNotSupportedForTarget<'a> {

compiler/rustc_session/src/session.rs

@@ -1302,6 +1302,12 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
             .emit_err(errors::SplitDebugInfoUnstablePlatform { debuginfo: sess.split_debuginfo() });
     }
 
+    let dwarf_version =
+        sess.opts.unstable_opts.dwarf_version.unwrap_or(sess.target.default_dwarf_version);
+    if sess.opts.cg.embed_source && dwarf_version < 5 {
+        sess.dcx().emit_err(errors::EmbedSourceInsufficientDwarfVersion { dwarf_version });
+    }
+
     if sess.opts.unstable_opts.instrument_xray.is_some() && !sess.target.options.supports_xray {
         sess.dcx().emit_err(errors::InstrumentationNotSupported { us: "XRay".to_string() });
     }

src/doc/rustc/src/codegen-options/index.md

@@ -148,7 +148,14 @@ at start-up, because the combination is invalid.
 
 ## embed-source
 
-TODO
+This flag controls whether the compiler embeds the program source code text into
+object debug info section. It takes one of the following values:
+
+* `y`, `yes`, `on` or `true`: put source code in debug info.
+* `n`, `no`, `off`, `false` or no value: omit source code from debug info (the default).
+
+`-C embed-source` requires DWARFv5. Use `-Zdwarf-version` to control the
+compiler's DWARF target version.
 
 ## extra-filename