[PATCH] libstdc++, Darwin: Do not use dev/null as the file for executables.

[Iain Sandoe]

Note that Windows-based platforms do something quite similar, but always
use the same (x.exe) filename.  I wonder, in passing, if that makes a
vulnerability in parallel testing (I chose to avoid the possibility for
Darwin).

Tested on x86_64-darwin21, x86_64-linux-gnu,
OK for trunk?
back-ports where applicable (I did not yet check)?
thanks
Iain

--- 8< ---

Darwin has a separate debug linker, which is invoked when the command
line contains source files and debug is enabled.

Using /dev/null as the executable name does not, therefore, work when
debug is enabled, since the debug linker does not accept /dev/null as
a valid executable name.

The leads to incorrectly UNSUPPORTED testcases because of the unintended
error result from the test compilation.

The solution here is to use a temporary file that is deleted at the
end of the test (which is the mechanism used elsewhere)

libstdc++-v3/ChangeLog:

        * testsuite/lib/libstdc++.exp (v3_target_compile): Instead of
        /dev/null, use a temporary file for test executables on Darwin.

Signed-off-by: Iain Sandoe <i...@sandoe.co.uk>
---
 libstdc++-v3/testsuite/lib/libstdc++.exp | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/lib/libstdc++.exp 
b/libstdc++-v3/testsuite/lib/libstdc++.exp
index 58804ecab26..4ae4cecb169 100644
--- a/libstdc++-v3/testsuite/lib/libstdc++.exp
+++ b/libstdc++-v3/testsuite/lib/libstdc++.exp
@@ -615,11 +615,15 @@ proc v3_target_compile { source dest type options } {
        }
     }
 
+    # For Windows and Darwin we might want to create a temporary file.
+    # note that it needs deleteting.
+    set file_to_delete ""
     # Small adjustment for Windows hosts.
     if { $dest == "/dev/null"
          && [info exists ::env(OS)] && [string match "Windows*" $::env(OS)] } {
        if { $type == "executable" } {
            set dest "x.exe"
+           set file_to_delete ${dest}
        } else {
            # Windows uses special file named "nul" as a substitute for
            # /dev/null
@@ -627,6 +631,15 @@ proc v3_target_compile { source dest type options } {
        }
     }
 
+    # Using /dev/null as the executable name does not work on Darwin when
+    # debug is enabled, since the debug linker does not accept /dev/null as
+    # a valid executable name.
+    if { $dest == "/dev/null" && [istarget *-*-darwin*]
+         && $type == "executable" } {
+       set dest dev-null-[pid].exe
+       set file_to_delete ${dest}
+    }
+
     lappend options "compiler=$cxx_final"
     lappend options "timeout=[timeout_value]"
 
@@ -637,7 +650,12 @@ proc v3_target_compile { source dest type options } {
     }
 
     set comp_output [target_compile $source $dest $type $options]
-
+    if { $type == "executable" && $file_to_delete != "" } {
+       file delete $file_to_delete
+       if { [istarget *-*-darwin*] && [file exists $file_to_delete.dSYM] } {
+           file delete -force $file_to_delete.dSYM
+       }
+    }
     return $comp_output
 }
 
-- 
2.39.2 (Apple Git-143)