Rollup merge of rust-lang#60769 - ehuss:rustc-cli-docs, r=steveklabnik

Update rustc book CLI docs.

This adds a little detail (and missing flags) to the rustc book. There is still a lot of information missing, but this seemed like a good step to expanding it.

Author: Centril

src/doc/rustc/src/command-line-arguments.md

@@ -17,28 +17,147 @@ to `#[cfg(verbose)]` and `#[cfg(feature = "serde")]` respectively.
 
 ## `-L`: add a directory to the library search path
 
-When looking for external crates, a directory passed to this flag will be searched.
+When looking for external crates or libraries, a directory passed to this flag
+will be searched.
+
+The kind of search path can optionally be specified with the form `-L
+KIND=PATH` where `KIND` may be one of:
+
+- `dependency` — Only search for transitive dependencies in this directory.
+- `crate` — Only search for this crate's direct dependencies in this
+  directory.
+- `native` — Only search for native libraries in this directory.
+- `framework` — Only search for macOS frameworks in this directory.
+- `all` — Search for all library kinds in this directory. This is the default
+  if `KIND` is not specified.
 
 ## `-l`: link the generated crate to a native library
 
 This flag allows you to specify linking to a specific native library when building
 a crate.
 
+The kind of library can optionally be specified with the form `-l KIND=lib`
+where `KIND` may be one of:
+
+- `dylib` — A native dynamic library.
+- `static` — A native static library (such as a `.a` archive).
+- `framework` — A macOS framework.
+
+The kind of library can be specified in a [`#[link]`
+attribute][link-attribute]. If the kind is not specified in the `link`
+attribute or on the command-line, it will link a dynamic library if available,
+otherwise it will use a static library. If the kind is specified on the
+command-line, it will override the kind specified in a `link` attribute.
+
+The name used in a `link` attribute may be overridden using the form `-l
+ATTR_NAME:LINK_NAME` where `ATTR_NAME` is the name in the `link` attribute,
+and `LINK_NAME` is the name of the actual library that will be linked.
+
+[link-attribute]: ../reference/items/external-blocks.html#the-link-attribute
+
 ## `--crate-type`: a list of types of crates for the compiler to emit
 
-This instructs `rustc` on which crate type to build.
+This instructs `rustc` on which crate type to build. This flag accepts a
+comma-separated list of values, and may be specified multiple times. The valid
+crate types are:
+
+- `lib` — Generates a library kind preferred by the compiler, currently
+  defaults to `rlib`.
+- `rlib` — A Rust static library.
+- `staticlib` — A native static library.
+- `dylib` — A Rust dynamic library.
+- `cdylib` — A native dynamic library.
+- `bin` — A runnable executable program.
+- `proc-macro` — Generates a format suitable for a procedural macro library
+  that may be loaded by the compiler.
+
+The crate type may be specified with the [`crate_type` attribute][crate_type].
+The `--crate-type` command-line value will override the `crate_type`
+attribute.
+
+More details may be found in the [linkage chapter] of the reference.
+
+[linkage chapter]: ../reference/linkage.html
+[crate_type]: ../reference/linkage.html
 
 ## `--crate-name`: specify the name of the crate being built
 
 This informs `rustc` of the name of your crate.
 
-## `--emit`: emit output other than a crate
-
-Instead of producing a crate, this flag can print out things like the assembly or LLVM-IR.
+## `--edition`: specify the edition to use
+
+This flag takes a value of `2015` or `2018`. The default is `2015`. More
+information about editions may be found in the [edition guide].
+
+[edition guide]: ../edition-guide/introduction.html
+
+## `--emit`: specifies the types of output files to generate
+
+This flag controls the types of output files generated by the compiler. It
+accepts a comma-separated list of values, and may be specified multiple times.
+The valid emit kinds are:
+
+- `asm` — Generates a file with the crate's assembly code. The default output
+  filename is `CRATE_NAME.s`.
+- `dep-info` — Generates a file with Makefile syntax that indicates all the
+  source files that were loaded to generate the crate. The default output
+  filename is `CRATE_NAME.d`.
+- `link` — Generates the crates specified by `--crate-type`. The default
+  output filenames depend on the crate type and platform. This is the default
+  if `--emit` is not specified.
+- `llvm-bc` — Generates a binary file containing the [LLVM bitcode]. The
+  default output filename is `CRATE_NAME.bc`.
+- `llvm-ir` — Generates a file containing [LLVM IR]. The default output
+  filename is `CRATE_NAME.ll`.
+- `metadata` — Generates a file containing metadata about the crate. The
+  default output filename is `CRATE_NAME.rmeta`.
+- `mir` — Generates a file containing rustc's mid-level intermediate
+  representation. The default output filename is `CRATE_NAME.mir`.
+- `obj` — Generates a native object file. The default output filename is
+  `CRATE_NAME.o`.
+
+The output filename can be set with the `-o` flag. A suffix may be added to
+the filename with the `-C extra-filename` flag. The files are written to the
+current directory unless the `--out-dir` flag is used. Each emission type may
+also specify the output filename with the form `KIND=PATH`, which takes
+precedence over the `-o` flag.
+
+[LLVM bitcode]: https://llvm.org/docs/BitCodeFormat.html
+[LLVM IR]: https://llvm.org/docs/LangRef.html
 
 ## `--print`: print compiler information
 
-This flag prints out various information about the compiler.
+This flag prints out various information about the compiler. This flag may be
+specified multiple times, and the information is printed in the order the
+flags are specified. Specifying a `--print` flag will usually disable the
+`--emit` step and will only print the requested information. The valid types
+of print values are:
+
+- `crate-name` — The name of the crate.
+- `file-names` — The names of the files created by the `link` emit kind.
+- `sysroot` — Path to the sysroot.
+- `cfg` — List of cfg values. See [conditional compilation] for more
+  information about cfg values.
+- `target-list` — List of known targets. The target may be selected with the
+  `--target` flag.
+- `target-cpus` — List of available CPU values for the current target. The
+  target CPU may be selected with the `-C target-cpu=val` flag.
+- `target-features` — List of available target features for the current
+  target. Target features may be enabled with the `-C target-feature=val`
+  flag.
+- `relocation-models` — List of relocation models. Relocation models may be
+  selected with the `-C relocation-model=val` flag.
+- `code-models` — List of code models. Code models may be selected with the
+  `-C code-model=val` flag.
+- `tls-models` — List of Thread Local Storage models supported. The model may
+  be selected with the `-Z tls-model=val` flag.
+- `native-static-libs` — This may be used when creating a `staticlib` crate
+  type. If this is the only flag, it will perform a full compilation and
+  include a diagnostic note that indicates the linker flags to use when
+  linking the resulting static library. The note starts with the text
+  `native-static-libs:` to make it easier to fetch the output.
+
+[conditional compilation]: ../reference/conditional-compilation.html
 
 ## `-g`: include debug information
 
@@ -54,7 +173,8 @@ This flag controls the output filename.
 
 ## `--out-dir`: directory to write the output in
 
-The outputted crate will be written to this directory.
+The outputted crate will be written to this directory. This flag is ignored if
+the `-o` flag is used.
 
 ## `--explain`: provide a detailed explanation of an error message
 
@@ -111,8 +231,9 @@ This flag, when combined with other flags, makes them produce extra output.
 
 ## `--extern`: specify where an external library is located
 
-This flag allows you to pass the name and location of an external crate that will
-be linked into the crate you're buildling.
+This flag allows you to pass the name and location of an external crate that
+will be linked into the crate you are building. This flag may be specified
+multiple times. The format of the value should be `CRATENAME=PATH`.
 
 ## `--sysroot`: Override the system root
 
@@ -121,8 +242,32 @@ distribution; this flag allows that to be overridden.
 
 ## `--error-format`: control how errors are produced
 
-This flag lets you control the format of errors.
+This flag lets you control the format of messages. Messages are printed to
+stderr. The valid options are:
+
+- `human` — Human-readable output. This is the default.
+- `json` — Structured JSON output.
+- `short` — Short, one-line messages.
 
 ## `--color`: configure coloring of output
 
-This flag lets you control color settings of the output.
+This flag lets you control color settings of the output. The valid options
+are:
+
+- `auto` — Use colors if output goes to a tty. This is the default.
+- `always` — Always use colors.
+- `never` — Never colorize output.
+
+## `--remap-path-prefix`: remap source names in output
+
+Remap source path prefixes in all output, including compiler diagnostics,
+debug information, macro expansions, etc. It takes a value of the form
+`FROM=TO` where a path prefix equal to `FROM` is rewritten to the value `TO`.
+The `FROM` may itself contain an `=` symbol, but the `TO` value may not. This
+flag may be specified multiple times.
+
+This is useful for normalizing build products, for example by removing the
+current directory out of pathnames emitted into the object files. The
+replacement is purely textual, with no consideration of the current system's
+pathname syntax. For example `--remap-path-prefix foo=bar` will match
+`foo/lib.rs` but not `./foo/lib.rs`.

src/librustc/session/config.rs

@@ -1744,8 +1744,7 @@ pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
         opt::multi_s(
             "",
             "print",
-            "Comma separated list of compiler information to \
-             print on stdout",
+            "Compiler information to print on stdout",
             "[crate-name|file-names|sysroot|cfg|target-list|\
              target-cpus|target-features|relocation-models|\
              code-models|tls-models|target-spec-json|native-static-libs]",