auto merge of #19144 : michaelwoerister/rust/lldb-scripts, r=alexcrichton

This PR adds the `rust-lldb` script (feel free to bikeshed about the name).
The script will start LLDB and, before doing anything else, load [LLDB type summaries](http://lldb.llvm.org/varformats.html) that will make LLDB print values with Rust syntax. Just use the script like you would normally use LLDB:

```
rust-lldb executable-to-debug --and-any-other-commandline --args 
```
The script will just add one additional commandline argument to the LLDB invocation and pass along the rest of the arguments to LLDB after that.

Given the following program...
```rust
fn main() {
	let x = Some(1u);
	let y = [0, 1, 2i];
	let z = (x, y);

	println!("{} {} {}", x, y, z);
}
```
...*without* the 'LLDB type summaries', values will be printed something like this...
```
(lldb) p x
(core::option::Option<uint>) $3 = {
   = (RUST$ENUM$DISR = Some)
   = (RUST$ENUM$DISR = Some, 1)
}
(lldb) p y
(long [3]) $4 = ([0] = 0, [1] = 1, [2] = 2)
(lldb) p z
((core::option::Option<uint>, [int, ..3])) $5 = {
   = {
     = (RUST$ENUM$DISR = Some)
     = (RUST$ENUM$DISR = Some, 1)
  }
   = ([0] = 0, [1] = 1, [2] = 2)
}
```
...*with* the 'LLDB type summaries', values will be printed like this:
```
(lldb) p x
(core::option::Option<uint>) $0 = Some(1)
(lldb) p y
(long [3]) $1 = [0, 1, 2]
(lldb) p z
((core::option::Option<uint>, [int, ..3])) $2 = (Some(1), [0, 1, 2])
```

The 'LLDB type summaries' used by the script have been in use for a while in the LLDB autotests but I still consider them to be of alpha-version quality. If you see anything weird when you use them, feel free to file an issue.

The script will use whatever Rust "installation" is in PATH, so whichever `rustc` will be called if you type `rustc` into the console, this is the one that the script will ask for the LLDB extension module location. The build system will take care of putting the script and LLDB python module in the right places, whether you want to use the stage1 or stage2 compiler or the one coming with `make install` / `rustup.sh`.

Since I don't have much experience with the build system, Makefiles and shell scripts, please look these changes over carefully.

9 files changed, 124 insertions, 12 deletions

diff --git a/Makefile.in b/Makefile.in
index 48b211167cf..17ae845bf07 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -198,6 +198,8 @@ include $(CFG_SRC_DIR)mk/rustllvm.mk
 include $(CFG_SRC_DIR)mk/docs.mk
 # LLVM
 include $(CFG_SRC_DIR)mk/llvm.mk
+# Rules for installing debugger scripts
+include $(CFG_SRC_DIR)mk/debuggers.mk
 
 ######################################################################
 # Secondary makefiles, conditionalized for speed
diff --git a/mk/clean.mk b/mk/clean.mk
index 97c823c9e2d..aadc55ba6c4 100644
--- a/mk/clean.mk
+++ b/mk/clean.mk
@@ -63,6 +63,7 @@ clean-generic-$(2)-$(1):
          -name '*.lib' -o \
          -name '*.dll' -o \
          -name '*.def' -o \
+         -name '*.py' -o \
          -name '*.bc' \
          \) \
          | xargs rm -f
@@ -78,7 +79,7 @@ define CLEAN_HOST_STAGE_N
 
 clean$(1)_H_$(2): \
 	    $$(foreach crate,$$(CRATES),clean$(1)_H_$(2)-lib-$$(crate)) \
-	    $$(foreach tool,$$(TOOLS),clean$(1)_H_$(2)-tool-$$(tool))
+	    $$(foreach tool,$$(TOOLS) $$(DEBUGGER_BIN_SCRIPTS),clean$(1)_H_$(2)-tool-$$(tool))
 	$$(Q)rm -fr $(2)/rt/libbacktrace
 
 clean$(1)_H_$(2)-tool-%:
@@ -98,7 +99,7 @@ define CLEAN_TARGET_STAGE_N
 
 clean$(1)_T_$(2)_H_$(3): \
 	    $$(foreach crate,$$(CRATES),clean$(1)_T_$(2)_H_$(3)-lib-$$(crate)) \
-	    $$(foreach tool,$$(TOOLS),clean$(1)_T_$(2)_H_$(3)-tool-$$(tool))
+	    $$(foreach tool,$$(TOOLS) $$(DEBUGGER_BIN_SCRIPTS),clean$(1)_T_$(2)_H_$(3)-tool-$$(tool))
 	$$(Q)rm -f $$(TLIB$(1)_T_$(2)_H_$(3))/libmorestack.a
 	$$(Q)rm -f $$(TLIB$(1)_T_$(2)_H_$(3))/libcompiler-rt.a
 	$(Q)rm -f $$(TLIB$(1)_T_$(2)_H_$(3))/librun_pass_stage* # For unix
diff --git a/mk/debuggers.mk b/mk/debuggers.mk
new file mode 100644
index 00000000000..54955f06295
--- /dev/null
+++ b/mk/debuggers.mk
@@ -0,0 +1,59 @@
+# Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution and at
+# http://rust-lang.org/COPYRIGHT.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+######################################################################
+# Copy debugger related scripts
+######################################################################
+
+DEBUGGER_RUSTLIB_ETC_SCRIPTS=lldb_rust_formatters.py
+DEBUGGER_BIN_SCRIPTS=rust-lldb
+
+DEBUGGER_RUSTLIB_ETC_SCRIPTS_ABS=$(foreach script,$(DEBUGGER_RUSTLIB_ETC_SCRIPTS), \
+                                     $(CFG_SRC_DIR)src/etc/$(script))
+DEBUGGER_BIN_SCRIPTS_ABS=$(foreach script,$(DEBUGGER_BIN_SCRIPTS), \
+                             $(CFG_SRC_DIR)src/etc/$(script))
+
+DEBUGGER_SCRIPTS_ALL=$(DEBUGGER_RUSTLIB_ETC_SCRIPTS_ABS) $(DEBUGGER_BIN_SCRIPTS_ABS)
+
+# $(1) - the stage to copy to
+# $(2) - the host triple
+define DEF_INSTALL_DEBUGGER_SCRIPTS_HOST
+
+tmp/install-debugger-scripts$(1)_H_$(2).done: $$(DEBUGGER_SCRIPTS_ALL)
+	$(Q)mkdir -p $$(HBIN$(1)_H_$(2))
+	$(Q)mkdir -p $$(HLIB$(1)_H_$(2))/rustlib/etc
+	$(Q)install $(DEBUGGER_BIN_SCRIPTS_ABS) $$(HBIN$(1)_H_$(2))
+	$(Q)install $(DEBUGGER_RUSTLIB_ETC_SCRIPTS_ABS) $$(HLIB$(1)_H_$(2))/rustlib/etc
+	$(Q)touch $$@
+endef
+
+# Expand host make-targets for all stages
+$(foreach stage,$(STAGES), \
+  $(foreach host,$(CFG_HOST), \
+    $(eval $(call DEF_INSTALL_DEBUGGER_SCRIPTS_HOST,$(stage),$(host)))))
+
+# $(1) is the stage number
+# $(2) is the target triple
+# $(3) is the host triple
+define DEF_INSTALL_DEBUGGER_SCRIPTS_TARGET
+
+tmp/install-debugger-scripts$(1)_T_$(2)_H_$(3).done: $$(DEBUGGER_SCRIPTS_ALL)
+	$(Q)mkdir -p $$(TBIN$(1)_T_$(2)_H_$(3))
+	$(Q)mkdir -p $$(TLIB$(1)_T_$(2)_H_$(3))/rustlib/etc
+	$(Q)install $(DEBUGGER_BIN_SCRIPTS_ABS) $$(TBIN$(1)_T_$(2)_H_$(3))
+	$(Q)install $(DEBUGGER_RUSTLIB_ETC_SCRIPTS_ABS) $$(TLIB$(1)_T_$(2)_H_$(3))/rustlib/etc
+	$(Q)touch $$@
+endef
+
+# Expand target make-targets for all stages
+$(foreach stage,$(STAGES), \
+  $(foreach target,$(CFG_TARGET), \
+    $(foreach host,$(CFG_HOST), \
+      $(eval $(call DEF_INSTALL_DEBUGGER_SCRIPTS_TARGET,$(stage),$(target),$(host))))))
diff --git a/mk/main.mk b/mk/main.mk
index a9a99f132fb..4aed1cea9ca 100644
--- a/mk/main.mk
+++ b/mk/main.mk
@@ -356,7 +356,8 @@ HSREQ$(1)_H_$(3) = $$(HBIN$(1)_H_$(3))/rustc$$(X_$(3))
 else
 HSREQ$(1)_H_$(3) = \
 	$$(HBIN$(1)_H_$(3))/rustc$$(X_$(3)) \
-	$$(MKFILE_DEPS)
+	$$(MKFILE_DEPS) \
+	tmp/install-debugger-scripts$(1)_H_$(3).done
 endif
 
 # Prerequisites for using the stageN compiler to build target artifacts
@@ -370,7 +371,8 @@ TSREQ$(1)_T_$(2)_H_$(3) = \
 SREQ$(1)_T_$(2)_H_$(3) = \
 	$$(TSREQ$(1)_T_$(2)_H_$(3)) \
 	$$(foreach dep,$$(TARGET_CRATES), \
-	    $$(TLIB$(1)_T_$(2)_H_$(3))/stamp.$$(dep))
+	    $$(TLIB$(1)_T_$(2)_H_$(3))/stamp.$$(dep)) \
+	tmp/install-debugger-scripts$(1)_T_$(2)_H_$(3).done
 
 # Prerequisites for a working stageN compiler and complete set of target
 # libraries
diff --git a/mk/prepare.mk b/mk/prepare.mk
index 7df2489744b..d404d3d2950 100644
--- a/mk/prepare.mk
+++ b/mk/prepare.mk
@@ -155,7 +155,7 @@ prepare-base-$(1): PREPARE_DEST_LIB_DIR=$$(PREPARE_DEST_DIR)/$$(CFG_LIBDIR_RELAT
 prepare-base-$(1): PREPARE_DEST_MAN_DIR=$$(PREPARE_DEST_DIR)/share/man/man1
 prepare-base-$(1): prepare-everything-$(1)
 
-prepare-everything-$(1): prepare-host-$(1) prepare-targets-$(1)
+prepare-everything-$(1): prepare-host-$(1) prepare-targets-$(1) prepare-debugger-scripts-$(1)
 
 prepare-host-$(1): prepare-host-tools-$(1)
 
@@ -167,8 +167,13 @@ prepare-host-tools-$(1): \
 prepare-host-dirs-$(1): prepare-maybe-clean-$(1)
 	$$(call PREPARE_DIR,$$(PREPARE_DEST_BIN_DIR))
 	$$(call PREPARE_DIR,$$(PREPARE_DEST_LIB_DIR))
+	$$(call PREPARE_DIR,$$(PREPARE_DEST_LIB_DIR)/rustlib/etc)
 	$$(call PREPARE_DIR,$$(PREPARE_DEST_MAN_DIR))
 
+prepare-debugger-scripts-$(1): prepare-host-dirs-$(1) $(DEBUGGER_SCRIPTS_ALL)
+	$$(Q)$$(PREPARE_BIN_CMD) $(DEBUGGER_BIN_SCRIPTS_ABS) $$(PREPARE_DEST_BIN_DIR)
+	$$(Q)$$(PREPARE_LIB_CMD) $(DEBUGGER_RUSTLIB_ETC_SCRIPTS_ABS) $$(PREPARE_DEST_LIB_DIR)/rustlib/etc
+
 $$(foreach tool,$$(PREPARE_TOOLS), \
   $$(foreach host,$$(CFG_HOST), \
       $$(eval $$(call DEF_PREPARE_HOST_TOOL,$$(tool),$$(PREPARE_STAGE),$$(host),$(1)))))
diff --git a/src/etc/lldb_rust_formatters.py b/src/etc/lldb_rust_formatters.py
index 642235ed4e3..7924d63c8e0 100644
--- a/src/etc/lldb_rust_formatters.py
+++ b/src/etc/lldb_rust_formatters.py
@@ -69,8 +69,14 @@ def print_struct_val_starting_from(field_start_index, val, internal_dict):
   assert val.GetType().GetTypeClass() == lldb.eTypeClassStruct
 
   t = val.GetType()
-  has_field_names = type_has_field_names(t)
   type_name = extract_type_name(t.GetName())
+  num_children = val.num_children
+
+  if (num_children - field_start_index) == 0:
+    # The only field of this struct is the enum discriminant
+    return type_name
+
+  has_field_names = type_has_field_names(t)
 
   if has_field_names:
       template = "%(type_name)s {\n%(body)s\n}"
@@ -83,8 +89,6 @@ def print_struct_val_starting_from(field_start_index, val, internal_dict):
     # this is a tuple, so don't print the type name
     type_name = ""
 
-  num_children = val.num_children
-
   def render_child(child_index):
     this = ""
     if has_field_names:
@@ -105,7 +109,6 @@ def print_enum_val(val, internal_dict):
 
   assert val.GetType().GetTypeClass() == lldb.eTypeClassUnion
 
-
   if val.num_children == 1:
     # This is either an enum with just one variant, or it is an Option-like enum
     # where the discriminant is encoded in a non-nullable pointer field. We find
diff --git a/src/etc/rust-lldb b/src/etc/rust-lldb
new file mode 100755
index 00000000000..19f36df7dba
--- /dev/null
+++ b/src/etc/rust-lldb
@@ -0,0 +1,30 @@
+#!/bin/sh
+# Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution and at
+# http://rust-lang.org/COPYRIGHT.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+# Exit if anything fails
+set -e
+
+# Create a tempfile containing the LLDB script we want to execute on startup
+TMPFILE=`mktemp /tmp/rust-lldb-commands.XXXXXX`
+
+# Make sure to delete the tempfile no matter what
+trap "rm -f $TMPFILE; exit" INT TERM EXIT
+
+# Find out where to look for the pretty printer Python module
+RUSTC_SYSROOT=`rustc -Zprint-sysroot`
+
+# Write the LLDB script to the tempfile
+echo "command script import \"$RUSTC_SYSROOT/lib/rustlib/etc/lldb_rust_formatters.py\"" >> $TMPFILE
+echo "type summary add --no-value --python-function lldb_rust_formatters.print_val -x \".*\" --category Rust" >> $TMPFILE
+echo "type category enable Rust" >> $TMPFILE
+
+# Call LLDB with the script added to the argument list
+lldb --source-before-file="$TMPFILE" "$@"
diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 82cf8f28e3d..8b4918b6db0 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -212,13 +212,14 @@ debugging_opts!(
         FLOWGRAPH_PRINT_LOANS,
         FLOWGRAPH_PRINT_MOVES,
         FLOWGRAPH_PRINT_ASSIGNS,
-        FLOWGRAPH_PRINT_ALL
+        FLOWGRAPH_PRINT_ALL,
+        PRINT_SYSROOT
     ]
     0
 )
 
 pub fn debugging_opts_map() -> Vec<(&'static str, &'static str, u64)> {
-    vec!(("verbose", "in general, enable more debug printouts", VERBOSE),
+    vec![("verbose", "in general, enable more debug printouts", VERBOSE),
      ("time-passes", "measure time of each rustc pass", TIME_PASSES),
      ("count-llvm-insns", "count where LLVM \
                            instrs originate", COUNT_LLVM_INSNS),
@@ -256,7 +257,9 @@ pub fn debugging_opts_map() -> Vec<(&'static str, &'static str, u64)> {
      ("flowgraph-print-assigns", "Include assignment analysis data in \
                        --pretty flowgraph output", FLOWGRAPH_PRINT_ASSIGNS),
      ("flowgraph-print-all", "Include all dataflow analysis data in \
-                       --pretty flowgraph output", FLOWGRAPH_PRINT_ALL))
+                       --pretty flowgraph output", FLOWGRAPH_PRINT_ALL),
+     ("print-sysroot", "Print the sysroot as used by this rustc invocation",
+      PRINT_SYSROOT)]
 }
 
 #[deriving(Clone)]
diff --git a/src/librustc_trans/driver/mod.rs b/src/librustc_trans/driver/mod.rs
index af5983244df..658be9169af 100644
--- a/src/librustc_trans/driver/mod.rs
+++ b/src/librustc_trans/driver/mod.rs
@@ -75,6 +75,13 @@ fn run_compiler(args: &[String]) {
                 describe_lints(&ls, false);
                 return;
             }
+
+            let sess = build_session(sopts, None, descriptions);
+            if sess.debugging_opt(config::PRINT_SYSROOT) {
+                println!("{}", sess.sysroot().display());
+                return;
+            }
+
             early_error("no input filename given");
         }
         1u => {