[PATCH 2/3] Add Rust support to default_target_compile

[Tom Tromey]

This adds support for the Rust language to default_target_compile.
This comes from a gdb patch:

    commit 67218854b1987d89593ccaf5feaf5b29b1b976f2
    Author: Tom Tromey <tom@tromey.com>
    Date:   Tue Apr 26 19:38:43 2016 -0600

        Update gdb test suite for Rust
    [...]
        2016-05-17  Tom Tromey  <tom@tromey.com>
                    Manish Goregaokar <manishsmail@gmail.com>
---
 ChangeLog        |  7 +++++++
 doc/dejagnu.texi |  5 +++++
 lib/libgloss.exp | 16 ++++++++++++++++
 lib/target.exp   | 25 ++++++++++++++++++++++++-
 4 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 216b4ec..b775c8f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2020-06-19  Tom Tromey  <tromey@adacore.com>
+
+       * doc/dejagnu.texi (target_compile procedure): Document rust
+       additions.
+       * lib/target.exp (default_target_compile): Handle rust.
+       * lib/libgloss.exp (find_rustc): New proc.
+
 2020-06-19  Tom Tromey  <tromey@adacore.com>
 
        * lib/target.exp (default_target_compile): Add early_flags.
diff --git a/doc/dejagnu.texi b/doc/dejagnu.texi
index fd7f16f..5052497 100644
--- a/doc/dejagnu.texi
+++ b/doc/dejagnu.texi
@@ -4564,6 +4564,8 @@ Use a compiler for the D language.
 Use a compiler for Fortran 77.
 @item f90
 Use a compiler for Fortran 90.
+@item rust
+Use a compiler for Rust.
 @end table
 If none of these options are given, the C compiler is used by default.
 Giving multiple language-selection options is an error.
@@ -4670,6 +4672,9 @@ compiler will be used and the @code{compiler} option 
ignored.
 @item F90_FOR_TARGET
 Override Fortran 90 compiler.  If the @code{f90} option is given, this
 compiler will be used and the @code{compiler} option ignored.
+@item RUSTC_FOR_TARGET
+Override Rust compiler.  If the @code{rust} option is given, this
+compiler will be used and the @code{compiler} option ignored.
 @item GNATMAKE_FOR_TARGET
 Override Ada compiler.  If the @code{ada} option is given, this
 compiler will be used and the @code{compiler} option ignored.
diff --git a/lib/libgloss.exp b/lib/libgloss.exp
index 56a9728..522e864 100644
--- a/lib/libgloss.exp
+++ b/lib/libgloss.exp
@@ -765,6 +765,22 @@ proc find_gnatmake {} {
     return $CC
 }
 
+proc find_rustc {} {
+    global tool_root_dir
+    if {![is_remote host]} {
+       set rustc [lookfor_file $tool_root_dir rustc]
+       if {$rustc eq ""} {
+           set rustc rustc
+       }
+    } else {
+       set rustc ""
+    }
+    if {$rustc ne ""} {
+       append rustc " --color never"
+    }
+    return $rustc
+}
+
 proc find_nm {} {
     global tool_root_dir
 
diff --git a/lib/target.exp b/lib/target.exp
index c98fbd0..132c1a3 100644
--- a/lib/target.exp
+++ b/lib/target.exp
@@ -400,6 +400,18 @@ proc default_target_compile {source destfile type options} 
{
            }
        }
 
+       if { $i eq "rust" } {
+           set compiler_type "rust"
+           if {[board_info $dest exists rustflags]} {
+               append add_flags " [board_info $dest rustflags]"
+           }
+           if {[board_info $dest exists rustcompiler]} {
+               set compiler [board_info $dest rustcompiler]
+           } else {
+               set compiler [find_rustc]
+           }
+       }
+
        if {[regexp "^dest=" $i]} {
            regsub "^dest=" $i "" tmp
            if {[board_info $tmp exists name]} {
@@ -460,6 +472,7 @@ proc default_target_compile {source destfile type options} {
     global F77_FOR_TARGET
     global F90_FOR_TARGET
     global GNATMAKE_FOR_TARGET
+    global RUSTC_FOR_TARGET
 
     if {[info exists GNATMAKE_FOR_TARGET]} {
        if { $compiler_type eq "ada" } {
@@ -497,6 +510,12 @@ proc default_target_compile {source destfile type options} 
{
        }
     }
 
+    if {[info exists RUSTC_FOR_TARGET]} {
+       if {$compiler_type eq "rust"} {
+           set compiler $RUSTC_FOR_TARGET
+       }
+    }
+
     if { $compiler eq "" } {
        if { [board_info $dest exists compiler] } {
            set compiler [board_info $dest compiler]
@@ -515,7 +534,11 @@ proc default_target_compile {source destfile type options} 
{
     }
 
     if {$type eq "object"} {
-       append add_flags " -c"
+       if {$compiler_type eq "rust"} {
+           append add_flags "--emit obj"
+       } else {
+           append add_flags " -c"
+       }
     }
 
     if { $type eq "preprocess" } {
-- 
2.21.3