[gcc r13-1232] libstdc++: testsuite: avoid predictable mkstemp

[gcc r13-1232] libstdc++: testsuite: avoid predictable mkstemp

[Alexandre Oliva]

https://gcc.gnu.org/g:2b86788d7c976a261446654166291e855cdc8191

commit r13-1232-g2b86788d7c976a261446654166291e855cdc8191
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu Jun 23 23:20:47 2022 -0300

    libstdc++: testsuite: avoid predictable mkstemp
    
    This patch was originally meant to reduce the likelihood that
    nonexistent_path() returns the same pathname for from and to.
    
    It was prompted by a target system with a non-random implementation of
    mkstemp, that returns a predictable sequence of filenames and selects
    the first one that isn't already taken.
    
    That turned out not to be enough: nonexistent_path adds a suffix to
    the filename chosen by mkstemp and removes the file it created, so
    mkstemp may very well insist on the same basename, and the case that
    doesn't use mkstemp doesn't even check whether the file already
    exists.
    
    Anyway, by the time I realized this wasn't enough, I'd already
    implemented some of the changes, and I figured I might as well
    contribute them, even though they don't really solve any problem, and
    even if they did, they'd be just a partial solution.
    
    
    for  libstdc++-v3/ChangeLog
    
            * testsuite/27_io/filesystem/operations/copy.cc (test02):
            Select TO after creating FROM.
            (test03, test04): Likewise.
            * testsuite/experimental/filesystem/operations/copy.cc
            (test02, test03, test04): Likewise.

Diff:
---
 libstdc++-v3/testsuite/27_io/filesystem/operations/copy.cc        | 7 ++++---
 libstdc++-v3/testsuite/experimental/filesystem/operations/copy.cc | 7 ++++---
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/libstdc++-v3/testsuite/27_io/filesystem/operations/copy.cc b/libstdc++-v3/testsuite/27_io/filesystem/operations/copy.cc
index b936e04493b..f3081f4b64e 100644
--- a/libstdc++-v3/testsuite/27_io/filesystem/operations/copy.cc
+++ b/libstdc++-v3/testsuite/27_io/filesystem/operations/copy.cc
@@ -73,7 +73,6 @@ test02()
 
   const std::error_code bad_ec = make_error_code(std::errc::invalid_argument);
   auto from = __gnu_test::nonexistent_path();
-  auto to = __gnu_test::nonexistent_path();
   std::error_code ec;
 
   ec = bad_ec;
@@ -81,6 +80,7 @@ test02()
   VERIFY( !ec );
   VERIFY( fs::exists(from) );
 
+  auto to = __gnu_test::nonexistent_path();
   ec = bad_ec;
   fs::copy(from, to, fs::copy_options::skip_symlinks, ec);
   VERIFY( !ec );
@@ -117,12 +117,13 @@ void
 test03()
 {
   auto from = __gnu_test::nonexistent_path();
-  auto to = __gnu_test::nonexistent_path();
 
   // test empty file
   std::ofstream{from};
   VERIFY( fs::exists(from) );
   VERIFY( fs::file_size(from) == 0 );
+
+  auto to = __gnu_test::nonexistent_path();
   fs::copy(from, to);
   VERIFY( fs::exists(to) );
   VERIFY( fs::file_size(to) == 0 );
@@ -145,11 +146,11 @@ test04()
 {
   const std::error_code bad_ec = make_error_code(std::errc::invalid_argument);
   auto from = __gnu_test::nonexistent_path();
-  auto to = __gnu_test::nonexistent_path();
   std::error_code ec;
 
   create_directories(from/"a/b/c");
 
+  auto to = __gnu_test::nonexistent_path();
   {
     __gnu_test::scoped_file f(to);
     copy(from, to, ec);
diff --git a/libstdc++-v3/testsuite/experimental/filesystem/operations/copy.cc b/libstdc++-v3/testsuite/experimental/filesystem/operations/copy.cc
index 5cd6b483c26..ca38328c5da 100644
--- a/libstdc++-v3/testsuite/experimental/filesystem/operations/copy.cc
+++ b/libstdc++-v3/testsuite/experimental/filesystem/operations/copy.cc
@@ -73,7 +73,6 @@ test02()
 #endif
 
   auto from = __gnu_test::nonexistent_path();
-  auto to = __gnu_test::nonexistent_path();
   std::error_code ec, bad = std::make_error_code(std::errc::invalid_argument);
 
   ec = bad;
@@ -81,6 +80,7 @@ test02()
   VERIFY( !ec );
   VERIFY( fs::exists(from) );
 
+  auto to = __gnu_test::nonexistent_path();
   ec = bad;
   fs::copy(from, to, fs::copy_options::skip_symlinks, ec);
   VERIFY( !ec );
@@ -116,12 +116,13 @@ void
 test03()
 {
   auto from = __gnu_test::nonexistent_path();
-  auto to = __gnu_test::nonexistent_path();
 
   // test empty file
   std::ofstream{from.c_str()};
   VERIFY( fs::exists(from) );
   VERIFY( fs::file_size(from) == 0 );
+
+  auto to = __gnu_test::nonexistent_path();
   fs::copy(from, to);
   VERIFY( fs::exists(to) );
   VERIFY( fs::file_size(to) == 0 );
@@ -143,11 +144,11 @@ void
 test04()
 {
   auto from = __gnu_test::nonexistent_path();
-  auto to = __gnu_test::nonexistent_path();
   std::error_code ec;
 
   create_directories(from/"a/b/c");
 
+  auto to = __gnu_test::nonexistent_path();
   {
     __gnu_test::scoped_file f(to);
     copy(from, to, ec);