Stop trying to use std::filesystem. (#1109)

There were problems with this that I couldn't figure out, and from more
reading, I get the impression that there's nobody designing it who does
know exactly how it's supposed to work.  There's no magic solution to
portability problems there, just new and unknown intricacies to replace
the old, somewhat-known ones.

Author: jtv

NEWS

@@ -1,6 +1,7 @@
 8.0.0-rc4
  - Release candidate for 8.0.0.
  - Any changes will be logged under "8.0.0".
+ - Stop trying to use/support `std::filesystem`.
 8.0.0
  - C++20 is now the oldest C++ version that libpqxx supports.
  - **Result/row iterators have changed.**  Instead of `i[n]` do `(*i)[n]`.

UPGRADING.md

@@ -321,10 +321,11 @@ All shell scripts now have a `.sh` suffix.  It takes some getting used to, but
 it simplifies some things such as running lint checkers on all of them without
 having to name each one of them individually.
 
-The build no longer tries to figure out whether it needs to link a standard C++
+The build no longer tries to figure out whether you need to link a standard C++
 filesystems library.  In most cases this seems to be part of the regular
-standard library now.  If you do need to add a link option to get
-`std::filesystem` to work, you'll have to pass that option yourself.
+standard library now, and at any rate libpqxx itself does not use it.  If you
+do need to add a link option to get `std::filesystem` to work, you'll have to
+pass that option yourself.
 
 In the lint script (now called `tools/lint.sh`), set `PQXX_LINT=skip` to skip
 lint checks.  This can speed up `make check` runs, and enable them to run

cmake/config.cmake

@@ -12,11 +12,6 @@ check_function_exists("poll" PQXX_HAVE_POLL)
 # Incorporate feature checks based on C++ feature test mac
 include(pqxx_cxx_feature_checks)
 
-# This variable is set by one of the snippets in config-tests.
-if(!no_need_fslib)
-    # TODO: This may work for gcc 8, but some clang versions may need -lc++fs.
-    link_libraries(stdc++fs)
-endif()
 set(AC_CONFIG_H_IN "${PROJECT_SOURCE_DIR}/include/pqxx/config.h.in")
 set(CM_CONFIG_H_IN "${PROJECT_BINARY_DIR}/include/pqxx/config_cmake.h.in")
 set(CM_CONFIG_PUB "${PROJECT_BINARY_DIR}/include/pqxx/config-public-compiler.h")

cmake/pqxx_cxx_feature_checks.cmake

@@ -103,6 +103,3 @@
 
 /* Version number of package */
 #undef VERSION
-
-/* Define if this feature is available. */
-#undef no_need_fslib

config-tests/no_need_fslib.cxx

@@ -12,7 +12,6 @@
 #define PQXX_H_ZVIEW
 
 #include <cassert>
-#include <filesystem>
 #include <string>
 #include <string_view>
 #include <type_traits>
@@ -113,15 +112,6 @@ public:
           zview(literal, size - 1)
   {}
 
-#if !defined(_WIN32)
-  /// Construct a `zview` from a `std::filesystem::path`.
-  /** @warn We don't currently support this on Windows, where encoding is a
-   * somewhat complicated question.  Answers on the internet often seem
-   * contradictory.
-   */
-  zview(std::filesystem::path const &p) : zview(p.c_str()) {}
-#endif // _WIN32
-
   /// Either a null pointer, or a zero-terminated text buffer.
   [[nodiscard]] constexpr char const *c_str() const & noexcept
   {

configure

@@ -129,14 +129,4 @@ AC_COMPILE_IFELSE(
         [Define if this feature is available.]),
     PQXX_HAVE_ZARGS=no)
 AC_MSG_RESULT($PQXX_HAVE_ZARGS)
-AC_MSG_CHECKING([no_need_fslib])
-no_need_fslib=yes
-AC_COMPILE_IFELSE(
-    [read_test(no_need_fslib.cxx)],
-    AC_DEFINE(
-        [no_need_fslib],
-        1,
-        [Define if this feature is available.]),
-    no_need_fslib=no)
-AC_MSG_RESULT($no_need_fslib)
 # End of config.

include/pqxx/config.h.in

@@ -1,5 +1,4 @@
 #include <cstdio>
-#include <filesystem>
 
 #include <pqxx/blob>
 #include <pqxx/transaction>
@@ -609,25 +608,6 @@ void test_blob_close_leaves_blob_unusable()
 }
 
 
-void test_blob_accepts_std_filesystem_path()
-{
-#if !defined(_WIN32)
-  char const temp_file[] = "blob-test-filesystem-path.tmp";
-  pqxx::bytes const data{std::byte{'4'}, std::byte{'2'}};
-
-  pqxx::connection cx;
-  pqxx::work tx{cx};
-  pqxx::bytes buf;
-
-  TempFile const f{std::data(temp_file), data};
-  std::filesystem::path const path{temp_file};
-  auto id{pqxx::blob::from_file(tx, path)};
-  pqxx::blob::to_buf(tx, id, buf, 10);
-  PQXX_CHECK_EQUAL(buf, data);
-#endif // _WIN32
-}
-
-
 PQXX_REGISTER_TEST(test_blob_is_useless_by_default);
 PQXX_REGISTER_TEST(test_blob_create_makes_empty_blob);
 PQXX_REGISTER_TEST(test_blob_create_with_oid_requires_oid_be_free);
@@ -655,5 +635,4 @@ PQXX_REGISTER_TEST(test_blob_from_file_with_oid_writes_blob);
 PQXX_REGISTER_TEST(test_blob_append_to_buf_appends);
 PQXX_REGISTER_TEST(test_blob_to_file_writes_file);
 PQXX_REGISTER_TEST(test_blob_close_leaves_blob_unusable);
-PQXX_REGISTER_TEST(test_blob_accepts_std_filesystem_path);
 } // namespace