[PATCH] Avoid running one Rust test against older LLVM

[PATCH] Avoid running one Rust test against older LLVM

[Tom Tromey]

LLVM 8.0 introduced some changes to let the Rust compiler emit DWARF
variant parts.  Before this change, the compiler would emit two types
with the same name, and unfortunately gdb happens to pick the wrong
one.  So, this patch disables the test when using an older version of
LLVM.

gdb/testsuite/ChangeLog
2020-09-10  Tom Tromey  <tromey@adacore.com>

	PR rust/26197:
	* lib/rust-support.exp (rust_llvm_version): New proc.
	* gdb.rust/simple.exp: Check rust_llvm_version.
---
 gdb/testsuite/ChangeLog            |  6 ++++++
 gdb/testsuite/gdb.rust/simple.exp  | 13 +++++++++++--
 gdb/testsuite/lib/rust-support.exp | 15 +++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/gdb/testsuite/gdb.rust/simple.exp b/gdb/testsuite/gdb.rust/simple.exp
index b32eaf1e4dc..882c2e07bcd 100644
--- a/gdb/testsuite/gdb.rust/simple.exp
+++ b/gdb/testsuite/gdb.rust/simple.exp
@@ -375,5 +375,14 @@ gdb_test "python print(e.type.fields()\[0\].artificial)" "True"
 gdb_test "python print(e.type.fields()\[1\].name)" "Two"
 
 gdb_test "python print(e.type.dynamic)" "False"
-gdb_test "python print(gdb.lookup_type('simple::MoreComplicated').dynamic)" \
-    "True"
+
+# Before LLVM 8, the rust compiler would emit two types named
+# "simple::MoreComplicated" -- the C-like "underlying" enum type and
+# the Rust enum.  lookup_type seems to get the former, which isn't
+# very useful.  With later versions of LLVM, this test works
+# correctly.
+set v [split [rust_llvm_version] .]
+if {[lindex $v 0] >= 8} {
+    gdb_test "python print(gdb.lookup_type('simple::MoreComplicated').dynamic)" \
+	"True"
+}
diff --git a/gdb/testsuite/lib/rust-support.exp b/gdb/testsuite/lib/rust-support.exp
index 72fba2623e9..b8157e8d104 100644
--- a/gdb/testsuite/lib/rust-support.exp
+++ b/gdb/testsuite/lib/rust-support.exp
@@ -35,3 +35,18 @@ proc gdb_compile_rust {sources dest options} {
     }
     return ""
 }
+
+# Return the version of LLVM used by the Rust compiler.  Note that
+# older versions of rustc don't print this -- in this case the
+# returned version is "0.0".
+gdb_caching_proc rust_llvm_version {
+    set rustc [find_rustc]
+    set output [lindex [remote_exec host "$rustc --version --verbose"] 1]
+    foreach line [split $output \n] {
+	if {[regexp "LLVM version: (.+)\$" $output ignore version]} {
+	    return $version
+	}
+    }
+    verbose "could not match rustc version output: $output"
+    return 0.0
+}
-- 
2.26.2

Re: [PATCH] Avoid running one Rust test against older LLVM

[Tom de Vries]

On 9/10/20 8:42 PM, Tom Tromey wrote:
> LLVM 8.0 introduced some changes to let the Rust compiler emit DWARF
> variant parts.  Before this change, the compiler would emit two types
> with the same name, and unfortunately gdb happens to pick the wrong
> one.  So, this patch disables the test when using an older version of
> LLVM.
> 

Works for me.

Tested with:
- rustc 1.36.0 with LLVM version 7.0
- rustc 1.45.2 with LLVM version: 9.0

Thanks,
- Tom

> gdb/testsuite/ChangeLog
> 2020-09-10  Tom Tromey  <tromey@adacore.com>
> 
> 	PR rust/26197:
> 	* lib/rust-support.exp (rust_llvm_version): New proc.
> 	* gdb.rust/simple.exp: Check rust_llvm_version.
> ---
>  gdb/testsuite/ChangeLog            |  6 ++++++
>  gdb/testsuite/gdb.rust/simple.exp  | 13 +++++++++++--
>  gdb/testsuite/lib/rust-support.exp | 15 +++++++++++++++
>  3 files changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.rust/simple.exp b/gdb/testsuite/gdb.rust/simple.exp
> index b32eaf1e4dc..882c2e07bcd 100644
> --- a/gdb/testsuite/gdb.rust/simple.exp
> +++ b/gdb/testsuite/gdb.rust/simple.exp
> @@ -375,5 +375,14 @@ gdb_test "python print(e.type.fields()\[0\].artificial)" "True"
>  gdb_test "python print(e.type.fields()\[1\].name)" "Two"
>  
>  gdb_test "python print(e.type.dynamic)" "False"
> -gdb_test "python print(gdb.lookup_type('simple::MoreComplicated').dynamic)" \
> -    "True"
> +
> +# Before LLVM 8, the rust compiler would emit two types named
> +# "simple::MoreComplicated" -- the C-like "underlying" enum type and
> +# the Rust enum.  lookup_type seems to get the former, which isn't
> +# very useful.  With later versions of LLVM, this test works
> +# correctly.
> +set v [split [rust_llvm_version] .]
> +if {[lindex $v 0] >= 8} {
> +    gdb_test "python print(gdb.lookup_type('simple::MoreComplicated').dynamic)" \
> +	"True"
> +}
> diff --git a/gdb/testsuite/lib/rust-support.exp b/gdb/testsuite/lib/rust-support.exp
> index 72fba2623e9..b8157e8d104 100644
> --- a/gdb/testsuite/lib/rust-support.exp
> +++ b/gdb/testsuite/lib/rust-support.exp
> @@ -35,3 +35,18 @@ proc gdb_compile_rust {sources dest options} {
>      }
>      return ""
>  }
> +
> +# Return the version of LLVM used by the Rust compiler.  Note that
> +# older versions of rustc don't print this -- in this case the
> +# returned version is "0.0".
> +gdb_caching_proc rust_llvm_version {
> +    set rustc [find_rustc]
> +    set output [lindex [remote_exec host "$rustc --version --verbose"] 1]
> +    foreach line [split $output \n] {
> +	if {[regexp "LLVM version: (.+)\$" $output ignore version]} {
> +	    return $version
> +	}
> +    }
> +    verbose "could not match rustc version output: $output"
> +    return 0.0
> +}
> 

Re: [PATCH] Avoid running one Rust test against older LLVM

[Pedro Alves]

On 9/10/20 7:42 PM, Tom Tromey wrote:

> +# Return the version of LLVM used by the Rust compiler.  Note that
> +# older versions of rustc don't print this -- in this case the
> +# returned version is "0.0".
> +gdb_caching_proc rust_llvm_version {
> +    set rustc [find_rustc]
> +    set output [lindex [remote_exec host "$rustc --version --verbose"] 1]

Pedantically I think it would be better to avoid executing
" --version --verbose" when find_rustc returns "".

Pedro Alves

> +    foreach line [split $output \n] {
> +	if {[regexp "LLVM version: (.+)\$" $output ignore version]} {
> +	    return $version
> +	}
> +    }
> +    verbose "could not match rustc version output: $output"
> +    return 0.0
> +}

Re: [PATCH] Avoid running one Rust test against older LLVM

[Tom Tromey]

>>>>> "Pedro" == Pedro Alves <pedro@palves.net> writes:

Pedro> On 9/10/20 7:42 PM, Tom Tromey wrote:
>> +# Return the version of LLVM used by the Rust compiler.  Note that
>> +# older versions of rustc don't print this -- in this case the
>> +# returned version is "0.0".
>> +gdb_caching_proc rust_llvm_version {
>> +    set rustc [find_rustc]
>> +    set output [lindex [remote_exec host "$rustc --version --verbose"] 1]

Pedro> Pedantically I think it would be better to avoid executing
Pedro> " --version --verbose" when find_rustc returns "".

Thanks, good idea.  I've updated it to handle this case.
I'm going to check it in now, and also on the gdb 10 branch.

Tom