[PATCH] libstdc++: testsuite: avoid predictable mkstemp

[Alexandre Oliva]

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.

Regstrapped on x86_64-linux-gnu, also tested with a cross to
aarch64-rtems6.  Ok to install?


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.
---
 .../testsuite/27_io/filesystem/operations/copy.cc  |    7 ++++---
 .../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 b936e04493b5c..f3081f4b64ebc 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 5cd6b483c269b..ca38328c5da15 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);

-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about <https://stallmansupport.org>