From 868212e4174fdf48672f4bb2e36efd3f7fda41d2 Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Tue, 29 Jun 2021 21:10:57 -0300
Subject: [PATCH 01/10] Optimize the file listing routine.

---
 src/fpm_filesystem.f90 | 242 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 241 insertions(+), 1 deletion(-)

diff --git a/src/fpm_filesystem.f90 b/src/fpm_filesystem.f90
index e6226b44ce..d2fcd95ac2 100644
--- a/src/fpm_filesystem.f90
+++ b/src/fpm_filesystem.f90
@@ -7,6 +7,8 @@ module fpm_filesystem
                                OS_CYGWIN, OS_SOLARIS, OS_FREEBSD, OS_OPENBSD
     use fpm_environment, only: separator, get_env
     use fpm_strings, only: f_string, replace, string_t, split
+    use iso_c_binding, only: c_int8_t, c_int16_t, c_int32_t, c_int64_t, c_int128_t, c_char, c_ptr, c_int, c_loc, c_long, c_short, &
+        c_null_char, c_associated, c_f_pointer
     implicit none
     private
     public :: basename, canon_path, dirname, is_dir, join_path, number_of_rows, read_lines, list_files, env_variable, &
@@ -16,6 +18,143 @@ module fpm_filesystem
 
     integer, parameter :: LINE_BUFFER_LEN = 1000
 
+#if (defined(MINGW64))
+    type, bind(c) :: stat_t
+        integer(kind=c_int32_t) :: st_dev
+        integer(kind=c_int16_t) :: st_ino
+        integer(kind=c_int16_t) :: st_mode
+        integer(kind=c_int16_t) :: st_nlink
+
+        integer(kind=c_int16_t) :: st_uid
+        integer(kind=c_int16_t) :: st_gid
+
+        integer(kind=c_int32_t) :: st_rdev
+        integer(kind=c_int32_t) :: st_size
+
+        integer(kind=c_int64_t) :: st_atime
+        integer(kind=c_int64_t) :: st_mtime
+        integer(kind=c_int64_t) :: st_ctime
+    end type
+#elif (defined(MINGW32))
+    type, bind(c) :: stat_t
+        integer(kind=c_int32_t) :: st_dev
+        integer(kind=c_int16_t) :: st_ino
+        integer(kind=c_int16_t) :: st_mode
+        integer(kind=c_int16_t) :: st_nlink
+
+        integer(kind=c_int16_t) :: st_uid
+        integer(kind=c_int16_t) :: st_gid
+
+        integer(kind=c_int32_t) :: st_rdev
+        integer(kind=c_int32_t) :: st_size
+
+        integer(kind=c_int32_t) :: st_atime
+        integer(kind=c_int32_t) :: st_mtime
+        integer(kind=c_int32_t) :: st_ctime
+    end type
+#elif (defined(LINUX64))
+    type, bind(c) :: stat_t
+        integer(kind=c_int64_t) :: st_dev
+        integer(kind=c_int64_t) :: st_ino
+        integer(kind=c_int64_t) :: st_nlink
+        integer(kind=c_int32_t) :: st_mode
+
+        integer(kind=c_int32_t) :: st_uid
+        integer(kind=c_int32_t) :: st_gid
+        integer(kind=c_int32_t) :: pad0
+
+        integer(kind=c_int64_t) :: st_rdev
+        integer(kind=c_int64_t) :: st_size
+        integer(kind=c_int64_t) :: st_blksize
+        integer(kind=c_int64_t) :: st_blocks
+
+        integer(kind=c_int128_t) :: st_atime
+        integer(kind=c_int128_t) :: st_mtime
+        integer(kind=c_int128_t) :: st_ctime
+
+        integer(kind=c_int64_t) :: glibc_reserved4
+        integer(kind=c_int64_t) :: glibc_reserved5
+        integer(kind=c_int64_t) :: glibc_reserved6
+    end type
+#elif (defined(LINUX32))
+    type, bind(c) :: stat_t
+        integer(kind=c_int64_t) :: st_dev
+        integer(kind=c_int16_t) :: pad1
+        integer(kind=c_int32_t) :: st_ino
+        integer(kind=c_int32_t) :: st_mode
+        integer(kind=c_int32_t) :: st_nlink
+
+        integer(kind=c_int32_t) :: st_uid
+        integer(kind=c_int32_t) :: st_gid
+        integer(kind=c_int64_t) :: st_rdev
+        integer(kind=c_int16_t) :: pad2
+
+        integer(kind=c_int32_t) :: st_size
+        integer(kind=c_int32_t) :: st_blksize
+        integer(kind=c_int32_t) :: st_blocks
+
+        integer(kind=c_int64_t) :: st_atime
+        integer(kind=c_int64_t) :: st_mtime
+        integer(kind=c_int64_t) :: st_ctime
+
+        integer(kind=c_int32_t) :: glibc_reserved4
+        integer(kind=c_int32_t) :: glibc_reserved5
+    end type
+#endif
+
+#if (defined(MINGW64) || defined(MINGW32))
+    type, bind(c) :: dirent
+        integer(kind=c_long)  :: d_ino
+        integer(kind=c_short) :: d_reclen
+        integer(kind=c_short) :: d_namlen
+        character(len=1,kind=c_char) :: d_name(260)
+    end type
+#elif (defined(LINUX64))
+    type, bind(c) :: dirent
+        integer(kind=c_int64_t) :: d_ino
+        integer(kind=c_int64_t) :: d_off
+        integer(kind=c_int16_t) :: d_reclen
+        integer(kind=c_int8_t)  :: d_type
+        character(len=1,kind=c_char) :: d_name(256)
+    end type
+#elif (defined(LINUX32))
+    type, bind(c) :: dirent
+        integer(kind=c_int32_t) :: d_ino
+        integer(kind=c_int32_t) :: d_off
+        integer(kind=c_int16_t) :: d_reclen
+        integer(kind=c_int8_t)  :: d_type
+        character(len=1,kind=c_char) :: d_name(256)
+    end type
+#endif
+
+#if (defined(MINGW64) || defined(MINGW32) || defined(LINUX64) || defined(LINUX32))
+    interface
+        function c_stat(path, buf) result(r) bind(c, name="stat")
+            import c_char, c_ptr, c_int
+            character(kind=c_char), intent(in) :: path(*)
+            type(c_ptr), value :: buf
+            integer(kind=c_int) :: r
+        end function c_stat
+
+        function c_opendir(dir) result(r) bind(c, name="opendir")
+            import c_char, c_ptr
+            character(kind=c_char), intent(in) :: dir(*)
+            type(c_ptr) :: r
+        end function c_opendir
+
+        function c_readdir(dir) result(r) bind(c, name="readdir")
+            import c_ptr
+            type(c_ptr), intent(in), value :: dir
+            type(c_ptr) :: r
+        end function c_readdir
+
+        function c_closedir(dir) result(r) bind(c, name="closedir")
+            import c_ptr, c_int
+            type(c_ptr), intent(in), value :: dir
+            integer(kind=c_int) :: r
+        end function c_closedir
+    end interface
+#endif
 
 contains
 
@@ -312,6 +451,107 @@ subroutine mkdir(dir)
 end subroutine mkdir
 
 
+#if (defined(MINGW64) || defined(MINGW32) || defined(LINUX64) || defined(LINUX32))
+!> Get file & directory names in directory `dir` using iso_c_binding.
+!!
+!!  - File/directory names return are relative to cwd, ie. preprended with `dir`
+!!  - Includes files starting with `.` except current directory and parent directory
+!!
+recursive subroutine list_files(dir, files, recurse)
+    character(len=*), intent(in) :: dir
+    type(string_t), allocatable, intent(out) :: files(:)
+    logical, intent(in), optional :: recurse
+
+    integer :: i
+    type(string_t), allocatable :: dir_files(:)
+    type(string_t), allocatable :: sub_dir_files(:)
+
+    type(c_ptr) :: dir_handle
+    type(c_ptr) :: dir_entry_c
+    type(dirent), pointer :: dir_entry_fortran
+    character(len=:), allocatable :: string_fortran
+    integer, parameter :: N_MAX = 256
+    type(string_t) :: files_tmp(N_MAX)
+    integer(kind=c_int) :: r
+
+    if (.not. is_dir_c(dir(1:len_trim(dir))//c_null_char)) then
+        allocate (files(0))
+        return
+    end if
+
+    dir_handle = c_opendir(dir(1:len_trim(dir))//c_null_char)
+    if (.not. c_associated(dir_handle)) then
+        print *, 'c_opendir() failed'
+        error stop
+    end if
+
+    i = 0
+    allocate(files(0))
+
+    do
+        dir_entry_c = c_readdir(dir_handle)
+        if (.not. c_associated(dir_entry_c)) then
+            exit
+        else
+            call c_f_pointer(dir_entry_c, dir_entry_fortran)
+            string_fortran = f_string(dir_entry_fortran%d_name)
+
+            if ((string_fortran .eq. '.' .or. string_fortran .eq. '..')) then
+                cycle
+            end if
+
+            i = i + 1
+
+            if (i .gt. N_MAX) then
+                files = [files, files_tmp]
+                i = 1
+            end if
+
+            files_tmp(i)%s = join_path(dir, string_fortran)
+        end if
+    end do
+
+    r = c_closedir(dir_handle)
+
+    if (r .ne. 0) then
+        print *, 'c_closedir() failed'
+        error stop
+    end if
+
+    if (i .gt. 0) then
+        files = [files, files_tmp(1:i)]
+    end if
+
+    if (present(recurse)) then
+        if (recurse) then
+
+            allocate(sub_dir_files(0))
+
+            do i=1,size(files)
+                if (is_dir_c(files(i)%s//c_null_char)) then
+                    call list_files(files(i)%s, dir_files, recurse=.true.)
+                    sub_dir_files = [sub_dir_files, dir_files]
+                end if
+            end do
+
+            files = [files, sub_dir_files]
+        end if
+    end if
+end subroutine list_files
+
+function is_dir_c(path) result(r)
+    character(kind=c_char), intent(in) :: path(*)
+    logical :: r
+    type(stat_t), target :: buf
+    integer(kind=c_int) :: exists
+    integer(kind=c_int), parameter :: S_IFMT  = 61440
+    integer(kind=c_int), parameter :: S_IFDIR = 16384
+
+    exists = c_stat(path, c_loc(buf))
+    r = exists .eq. 0 .and. iand(int(buf%st_mode, kind=c_int), S_IFMT) .eq. S_IFDIR
+end function is_dir_c
+
+#else
 !> Get file & directory names in directory `dir`.
 !!
 !!  - File/directory names return are relative to cwd, ie. preprended with `dir`
@@ -376,7 +616,7 @@ recursive subroutine list_files(dir, files, recurse)
     end if
 
 end subroutine list_files
-
+#endif
 
 !> test if pathname already exists
 logical function exists(filename) result(r)

From 7de24a6cf2a8bb13eda0a9921c6c5f9062fe159c Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Tue, 29 Jun 2021 21:15:42 -0300
Subject: [PATCH 02/10] Rename fpm_filesystem.f90 to fpm_filesystem.F90:
 requires preprocessor

---
 src/{fpm_filesystem.f90 => fpm_filesystem.F90} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename src/{fpm_filesystem.f90 => fpm_filesystem.F90} (100%)

diff --git a/src/fpm_filesystem.f90 b/src/fpm_filesystem.F90
similarity index 100%
rename from src/fpm_filesystem.f90
rename to src/fpm_filesystem.F90

From db869aa38ad7736df9eec5dfb8ac05b4ba45590b Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Wed, 7 Jul 2021 00:38:31 -0300
Subject: [PATCH 03/10] Add C wrapper for file listing

---
 src/c.c                |  22 +++++
 src/fpm_filesystem.F90 | 178 +++++++++--------------------------------
 src/fpm_strings.f90    |  32 ++++++++
 3 files changed, 91 insertions(+), 141 deletions(-)
 create mode 100644 src/c.c

diff --git a/src/c.c b/src/c.c
new file mode 100644
index 0000000000..8cfbd2024c
--- /dev/null
+++ b/src/c.c
@@ -0,0 +1,22 @@
+/* FIXME: fpm --flag '-DENABLE_C_WRAPPER' currently doesn't work with .c files. Use #if..#endif below for the time being. */
+#if ((defined(_WIN32) && (defined(__MINGW32__) || defined(__MINGW64__))) || defined(__linux__) || defined(__APPLE__) || defined(__OpenBSD__))
+#define ENABLE_C_WRAPPER
+#endif
+
+#ifdef ENABLE_C_WRAPPER
+#include <sys/stat.h>
+#include <dirent.h>
+
+int is_dir(const char *path)
+{
+    struct stat m;
+    int r = stat(path, &m);
+    return r == 0 && S_ISDIR(m.st_mode);
+}
+
+const char *get_d_name(struct dirent *d)
+{
+    return (const char *) d->d_name;
+}
+
+#endif
diff --git a/src/fpm_filesystem.F90 b/src/fpm_filesystem.F90
index d2fcd95ac2..7d21e31307 100644
--- a/src/fpm_filesystem.F90
+++ b/src/fpm_filesystem.F90
@@ -7,8 +7,7 @@ module fpm_filesystem
                                OS_CYGWIN, OS_SOLARIS, OS_FREEBSD, OS_OPENBSD
     use fpm_environment, only: separator, get_env
     use fpm_strings, only: f_string, replace, string_t, split
-    use iso_c_binding, only: c_int8_t, c_int16_t, c_int32_t, c_int64_t, c_int128_t, c_char, c_ptr, c_int, c_loc, c_long, c_short, &
-        c_null_char, c_associated, c_f_pointer
+    use iso_c_binding, only: c_char, c_ptr, c_int, c_null_char, c_associated, c_f_pointer
     implicit none
     private
     public :: basename, canon_path, dirname, is_dir, join_path, number_of_rows, read_lines, list_files, env_variable, &
@@ -18,124 +17,8 @@ module fpm_filesystem
 
     integer, parameter :: LINE_BUFFER_LEN = 1000
 
-#if (defined(MINGW64))
-    type, bind(c) :: stat_t
-        integer(kind=c_int32_t) :: st_dev
-        integer(kind=c_int16_t) :: st_ino
-        integer(kind=c_int16_t) :: st_mode
-        integer(kind=c_int16_t) :: st_nlink
-
-        integer(kind=c_int16_t) :: st_uid
-        integer(kind=c_int16_t) :: st_gid
-
-        integer(kind=c_int32_t) :: st_rdev
-        integer(kind=c_int32_t) :: st_size
-
-        integer(kind=c_int64_t) :: st_atime
-        integer(kind=c_int64_t) :: st_mtime
-        integer(kind=c_int64_t) :: st_ctime
-    end type
-#elif (defined(MINGW32))
-    type, bind(c) :: stat_t
-        integer(kind=c_int32_t) :: st_dev
-        integer(kind=c_int16_t) :: st_ino
-        integer(kind=c_int16_t) :: st_mode
-        integer(kind=c_int16_t) :: st_nlink
-
-        integer(kind=c_int16_t) :: st_uid
-        integer(kind=c_int16_t) :: st_gid
-
-        integer(kind=c_int32_t) :: st_rdev
-        integer(kind=c_int32_t) :: st_size
-
-        integer(kind=c_int32_t) :: st_atime
-        integer(kind=c_int32_t) :: st_mtime
-        integer(kind=c_int32_t) :: st_ctime
-    end type
-#elif (defined(LINUX64))
-    type, bind(c) :: stat_t
-        integer(kind=c_int64_t) :: st_dev
-        integer(kind=c_int64_t) :: st_ino
-        integer(kind=c_int64_t) :: st_nlink
-        integer(kind=c_int32_t) :: st_mode
-
-        integer(kind=c_int32_t) :: st_uid
-        integer(kind=c_int32_t) :: st_gid
-        integer(kind=c_int32_t) :: pad0
-
-        integer(kind=c_int64_t) :: st_rdev
-        integer(kind=c_int64_t) :: st_size
-        integer(kind=c_int64_t) :: st_blksize
-        integer(kind=c_int64_t) :: st_blocks
-
-        integer(kind=c_int128_t) :: st_atime
-        integer(kind=c_int128_t) :: st_mtime
-        integer(kind=c_int128_t) :: st_ctime
-
-        integer(kind=c_int64_t) :: glibc_reserved4
-        integer(kind=c_int64_t) :: glibc_reserved5
-        integer(kind=c_int64_t) :: glibc_reserved6
-    end type
-#elif (defined(LINUX32))
-    type, bind(c) :: stat_t
-        integer(kind=c_int64_t) :: st_dev
-        integer(kind=c_int16_t) :: pad1
-        integer(kind=c_int32_t) :: st_ino
-        integer(kind=c_int32_t) :: st_mode
-        integer(kind=c_int32_t) :: st_nlink
-
-        integer(kind=c_int32_t) :: st_uid
-        integer(kind=c_int32_t) :: st_gid
-        integer(kind=c_int64_t) :: st_rdev
-        integer(kind=c_int16_t) :: pad2
-
-        integer(kind=c_int32_t) :: st_size
-        integer(kind=c_int32_t) :: st_blksize
-        integer(kind=c_int32_t) :: st_blocks
-
-        integer(kind=c_int64_t) :: st_atime
-        integer(kind=c_int64_t) :: st_mtime
-        integer(kind=c_int64_t) :: st_ctime
-
-        integer(kind=c_int32_t) :: glibc_reserved4
-        integer(kind=c_int32_t) :: glibc_reserved5
-    end type
-#endif
-
-#if (defined(MINGW64) || defined(MINGW32))
-    type, bind(c) :: dirent
-        integer(kind=c_long)  :: d_ino
-        integer(kind=c_short) :: d_reclen
-        integer(kind=c_short) :: d_namlen
-        character(len=1,kind=c_char) :: d_name(260)
-    end type
-#elif (defined(LINUX64))
-    type, bind(c) :: dirent
-        integer(kind=c_int64_t) :: d_ino
-        integer(kind=c_int64_t) :: d_off
-        integer(kind=c_int16_t) :: d_reclen
-        integer(kind=c_int8_t)  :: d_type
-        character(len=1,kind=c_char) :: d_name(256)
-    end type
-#elif (defined(LINUX32))
-    type, bind(c) :: dirent
-        integer(kind=c_int32_t) :: d_ino
-        integer(kind=c_int32_t) :: d_off
-        integer(kind=c_int16_t) :: d_reclen
-        integer(kind=c_int8_t)  :: d_type
-        character(len=1,kind=c_char) :: d_name(256)
-    end type
-#endif
-
-#if (defined(MINGW64) || defined(MINGW32) || defined(LINUX64) || defined(LINUX32))
+#ifdef ENABLE_C_WRAPPER
     interface
-        function c_stat(path, buf) result(r) bind(c, name="stat")
-            import c_char, c_ptr, c_int
-            character(kind=c_char), intent(in) :: path(*)
-            type(c_ptr), value :: buf
-            integer(kind=c_int) :: r
-        end function c_stat
-
         function c_opendir(dir) result(r) bind(c, name="opendir")
             import c_char, c_ptr
             character(kind=c_char), intent(in) :: dir(*)
@@ -153,6 +36,18 @@ function c_closedir(dir) result(r) bind(c, name="closedir")
             type(c_ptr), intent(in), value :: dir
             integer(kind=c_int) :: r
         end function c_closedir
+
+        function c_get_d_name(dir) result(r) bind(c, name="get_d_name")
+            import c_ptr
+            type(c_ptr), intent(in), value :: dir
+            type(c_ptr) :: r
+        end function c_get_d_name
+
+        function c_is_dir(path) result(r) bind(c, name="is_dir")
+            import c_char, c_int
+            character(kind=c_char), intent(in) :: path(*)
+            integer(kind=c_int) :: r
+        end function c_is_dir
     end interface
 #endif
 
@@ -450,17 +345,17 @@ subroutine mkdir(dir)
     end if
 end subroutine mkdir
 
-
-#if (defined(MINGW64) || defined(MINGW32) || defined(LINUX64) || defined(LINUX32))
+#ifdef ENABLE_C_WRAPPER
 !> Get file & directory names in directory `dir` using iso_c_binding.
 !!
 !!  - File/directory names return are relative to cwd, ie. preprended with `dir`
 !!  - Includes files starting with `.` except current directory and parent directory
 !!
-recursive subroutine list_files(dir, files, recurse)
+recursive subroutine list_files(dir, files, recurse, separator)
     character(len=*), intent(in) :: dir
     type(string_t), allocatable, intent(out) :: files(:)
     logical, intent(in), optional :: recurse
+    character(len=1), optional :: separator
 
     integer :: i
     type(string_t), allocatable :: dir_files(:)
@@ -468,13 +363,25 @@ recursive subroutine list_files(dir, files, recurse)
 
     type(c_ptr) :: dir_handle
     type(c_ptr) :: dir_entry_c
-    type(dirent), pointer :: dir_entry_fortran
+    character(len=:,kind=c_char), allocatable :: fortran_name
     character(len=:), allocatable :: string_fortran
     integer, parameter :: N_MAX = 256
     type(string_t) :: files_tmp(N_MAX)
     integer(kind=c_int) :: r
+    character(len=1) :: filesep
+
+    if (present(separator)) then
+        filesep = separator
+    else
+        select case (get_os_type())
+            case default
+                filesep = '/'
+            case (OS_WINDOWS)
+                filesep = '\'
+        end select
+    end if
 
-    if (.not. is_dir_c(dir(1:len_trim(dir))//c_null_char)) then
+    if (c_is_dir(dir(1:len_trim(dir))//c_null_char) .eq. 0) then
         allocate (files(0))
         return
     end if
@@ -493,8 +400,7 @@ recursive subroutine list_files(dir, files, recurse)
         if (.not. c_associated(dir_entry_c)) then
             exit
         else
-            call c_f_pointer(dir_entry_c, dir_entry_fortran)
-            string_fortran = f_string(dir_entry_fortran%d_name)
+            string_fortran = f_string(c_get_d_name(dir_entry_c))
 
             if ((string_fortran .eq. '.' .or. string_fortran .eq. '..')) then
                 cycle
@@ -507,7 +413,7 @@ recursive subroutine list_files(dir, files, recurse)
                 i = 1
             end if
 
-            files_tmp(i)%s = join_path(dir, string_fortran)
+            files_tmp(i)%s = dir // filesep // string_fortran
         end if
     end do
 
@@ -528,8 +434,8 @@ recursive subroutine list_files(dir, files, recurse)
             allocate(sub_dir_files(0))
 
             do i=1,size(files)
-                if (is_dir_c(files(i)%s//c_null_char)) then
-                    call list_files(files(i)%s, dir_files, recurse=.true.)
+                if (c_is_dir(files(i)%s//c_null_char) .ne. 0) then
+                    call list_files(files(i)%s, dir_files, recurse=.true., separator=filesep)
                     sub_dir_files = [sub_dir_files, dir_files]
                 end if
             end do
@@ -539,18 +445,6 @@ recursive subroutine list_files(dir, files, recurse)
     end if
 end subroutine list_files
 
-function is_dir_c(path) result(r)
-    character(kind=c_char), intent(in) :: path(*)
-    logical :: r
-    type(stat_t), target :: buf
-    integer(kind=c_int) :: exists
-    integer(kind=c_int), parameter :: S_IFMT  = 61440
-    integer(kind=c_int), parameter :: S_IFDIR = 16384
-
-    exists = c_stat(path, c_loc(buf))
-    r = exists .eq. 0 .and. iand(int(buf%st_mode, kind=c_int), S_IFMT) .eq. S_IFDIR
-end function is_dir_c
-
 #else
 !> Get file & directory names in directory `dir`.
 !!
@@ -616,8 +510,10 @@ recursive subroutine list_files(dir, files, recurse)
     end if
 
 end subroutine list_files
+
 #endif
 
+
 !> test if pathname already exists
 logical function exists(filename) result(r)
     character(len=*), intent(in) :: filename
diff --git a/src/fpm_strings.f90 b/src/fpm_strings.f90
index 3d7d7b1a92..5a47311740 100644
--- a/src/fpm_strings.f90
+++ b/src/fpm_strings.f90
@@ -29,6 +29,7 @@
 
 module fpm_strings
 use iso_fortran_env, only: int64
+use iso_c_binding, only: c_char, c_ptr, c_int, c_null_char, c_associated, c_f_pointer, c_size_t
 implicit none
 
 private
@@ -70,6 +71,10 @@ module fpm_strings
     module procedure new_string_t
 end interface string_t
 
+interface f_string
+    module procedure f_string, f_string_cptr, f_string_cptr_n
+end interface f_string
+
 contains
 
 !> test if a CHARACTER string ends with a specified suffix
@@ -125,6 +130,33 @@ function f_string(c_string)
 end function f_string
 
 
+!> return Fortran character variable when given a null-terminated c_ptr
+function f_string_cptr(cptr) result(s)
+    type(c_ptr), intent(in), value :: cptr
+    character(len=:,kind=c_char), allocatable :: s
+
+    interface
+        function c_strlen(s) result(r) bind(c, name="strlen")
+            import c_size_t, c_ptr
+            type(c_ptr), intent(in), value :: s
+            integer(kind=c_size_t) :: r
+        end function
+    end interface
+
+    s = f_string_cptr_n(cptr, c_strlen(cptr))
+end function
+
+!> return Fortran character variable when given a null-terminated c_ptr and its length
+function f_string_cptr_n(cptr, n) result(s)
+    type(c_ptr), intent(in), value :: cptr
+    integer(kind=c_size_t), intent(in) :: n
+    character(len=n,kind=c_char) :: s
+    character(len=n,kind=c_char), pointer :: sptr
+
+    call c_f_pointer(cptr, sptr)
+    s = sptr
+end function
+
 !> Hash a character(*) string of default kind
 pure function fnv_1a_char(input, seed) result(hash)
     character(*), intent(in) :: input

From 52cb72f02e04786015b2adacd8072bcf2f5e89cb Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Sat, 10 Jul 2021 21:30:35 -0300
Subject: [PATCH 04/10] Use C wrapper by default

---
 src/c.c                | 8 --------
 src/fpm_filesystem.F90 | 4 ++--
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/src/c.c b/src/c.c
index 8cfbd2024c..c54469ab06 100644
--- a/src/c.c
+++ b/src/c.c
@@ -1,9 +1,3 @@
-/* FIXME: fpm --flag '-DENABLE_C_WRAPPER' currently doesn't work with .c files. Use #if..#endif below for the time being. */
-#if ((defined(_WIN32) && (defined(__MINGW32__) || defined(__MINGW64__))) || defined(__linux__) || defined(__APPLE__) || defined(__OpenBSD__))
-#define ENABLE_C_WRAPPER
-#endif
-
-#ifdef ENABLE_C_WRAPPER
 #include <sys/stat.h>
 #include <dirent.h>
 
@@ -18,5 +12,3 @@ const char *get_d_name(struct dirent *d)
 {
     return (const char *) d->d_name;
 }
-
-#endif
diff --git a/src/fpm_filesystem.F90 b/src/fpm_filesystem.F90
index 7d21e31307..7b70ebe47d 100644
--- a/src/fpm_filesystem.F90
+++ b/src/fpm_filesystem.F90
@@ -17,7 +17,7 @@ module fpm_filesystem
 
     integer, parameter :: LINE_BUFFER_LEN = 1000
 
-#ifdef ENABLE_C_WRAPPER
+#ifndef FPM_BOOTSTRAP
     interface
         function c_opendir(dir) result(r) bind(c, name="opendir")
             import c_char, c_ptr
@@ -345,7 +345,7 @@ subroutine mkdir(dir)
     end if
 end subroutine mkdir
 
-#ifdef ENABLE_C_WRAPPER
+#ifndef FPM_BOOTSTRAP
 !> Get file & directory names in directory `dir` using iso_c_binding.
 !!
 !!  - File/directory names return are relative to cwd, ie. preprended with `dir`

From 619d619bf5754437401c314521fd48ecd557a5a0 Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Sun, 11 Jul 2021 11:05:15 -0300
Subject: [PATCH 05/10] Rename C function is_dir to c_is_dir

---
 src/c.c                | 2 +-
 src/fpm_filesystem.F90 | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/c.c b/src/c.c
index c54469ab06..d9048a9a49 100644
--- a/src/c.c
+++ b/src/c.c
@@ -1,7 +1,7 @@
 #include <sys/stat.h>
 #include <dirent.h>
 
-int is_dir(const char *path)
+int c_is_dir(const char *path)
 {
     struct stat m;
     int r = stat(path, &m);
diff --git a/src/fpm_filesystem.F90 b/src/fpm_filesystem.F90
index 7b70ebe47d..9ae95cc81f 100644
--- a/src/fpm_filesystem.F90
+++ b/src/fpm_filesystem.F90
@@ -43,7 +43,7 @@ function c_get_d_name(dir) result(r) bind(c, name="get_d_name")
             type(c_ptr) :: r
         end function c_get_d_name
 
-        function c_is_dir(path) result(r) bind(c, name="is_dir")
+        function c_is_dir(path) result(r) bind(c, name="c_is_dir")
             import c_char, c_int
             character(kind=c_char), intent(in) :: path(*)
             integer(kind=c_int) :: r

From 53027990c205eb905ff534544f4752ea92e747d7 Mon Sep 17 00:00:00 2001
From: LKedward <laurence.kedward@bristol.ac.uk>
Date: Fri, 16 Jul 2021 15:14:22 +0100
Subject: [PATCH 06/10] Fix: dirent symbols for OSX.

---
 src/c.c                | 27 +++++++++++++++++++++++++++
 src/fpm_filesystem.F90 |  4 ++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/src/c.c b/src/c.c
index d9048a9a49..7075f4232b 100644
--- a/src/c.c
+++ b/src/c.c
@@ -1,6 +1,11 @@
 #include <sys/stat.h>
 #include <dirent.h>
 
+#ifdef __APPLE__
+DIR * opendir$INODE64( const char * dirName );
+struct dirent * readdir$INODE64( DIR * dir );
+#endif
+
 int c_is_dir(const char *path)
 {
     struct stat m;
@@ -12,3 +17,25 @@ const char *get_d_name(struct dirent *d)
 {
     return (const char *) d->d_name;
 }
+
+
+
+DIR *c_opendir(const char *dirname){
+
+#ifdef __APPLE__
+    return opendir$INODE64(dirname);
+#else
+    return opendir(dirname);
+#endif
+
+}
+
+struct dirent *c_readdir(DIR *dirp){
+
+#ifdef __APPLE__
+    return readdir$INODE64(dirp);
+#else
+    return readdir(dirp);
+#endif
+
+}
\ No newline at end of file
diff --git a/src/fpm_filesystem.F90 b/src/fpm_filesystem.F90
index 9ae95cc81f..2851bfd605 100644
--- a/src/fpm_filesystem.F90
+++ b/src/fpm_filesystem.F90
@@ -19,13 +19,13 @@ module fpm_filesystem
 
 #ifndef FPM_BOOTSTRAP
     interface
-        function c_opendir(dir) result(r) bind(c, name="opendir")
+        function c_opendir(dir) result(r) bind(c, name="c_opendir")
             import c_char, c_ptr
             character(kind=c_char), intent(in) :: dir(*)
             type(c_ptr) :: r
         end function c_opendir
 
-        function c_readdir(dir) result(r) bind(c, name="readdir")
+        function c_readdir(dir) result(r) bind(c, name="c_readdir")
             import c_ptr
             type(c_ptr), intent(in), value :: dir
             type(c_ptr) :: r

From e18017d155c7edb31a503203187c5d0bab20b846 Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Fri, 16 Jul 2021 21:15:47 -0300
Subject: [PATCH 07/10] Rename src\c.c => src\filesystem_utilities.c

---
 src/{c.c => filesystem_utilities.c} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename src/{c.c => filesystem_utilities.c} (100%)

diff --git a/src/c.c b/src/filesystem_utilities.c
similarity index 100%
rename from src/c.c
rename to src/filesystem_utilities.c

From 1c6673c62523d7a3cf8bfa37e8997da8e76b7f9c Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Tue, 20 Jul 2021 00:00:51 -0300
Subject: [PATCH 08/10] Cache get_os_type() return value using the save
 attribute

---
 src/fpm_environment.f90 | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/fpm_environment.f90 b/src/fpm_environment.f90
index e9da3c76a2..a9f8c65972 100644
--- a/src/fpm_environment.f90
+++ b/src/fpm_environment.f90
@@ -40,7 +40,16 @@ integer function get_os_type() result(r)
         character(len=32) :: val
         integer           :: length, rc
         logical           :: file_exists
+        logical, save     :: first_run = .true.
+        integer, save     :: ret = OS_UNKNOWN
+        !omp threadprivate(ret, first_run)
 
+        if (.not. first_run) then
+            r = ret
+            return
+        end if
+
+        first_run = .false.
         r = OS_UNKNOWN
 
         ! Check environment variable `OS`.
@@ -48,6 +57,7 @@ integer function get_os_type() result(r)
 
         if (rc == 0 .and. length > 0 .and. index(val, 'Windows_NT') > 0) then
             r = OS_WINDOWS
+            ret = r
             return
         end if
 
@@ -58,42 +68,49 @@ integer function get_os_type() result(r)
             ! Linux
             if (index(val, 'linux') > 0) then
                 r = OS_LINUX
+                ret = r
                 return
             end if
 
             ! macOS
             if (index(val, 'darwin') > 0) then
                 r = OS_MACOS
+                ret = r
                 return
             end if
 
             ! Windows, MSYS, MinGW, Git Bash
             if (index(val, 'win') > 0 .or. index(val, 'msys') > 0) then
                 r = OS_WINDOWS
+                ret = r
                 return
             end if
 
             ! Cygwin
             if (index(val, 'cygwin') > 0) then
                 r = OS_CYGWIN
+                ret = r
                 return
             end if
 
             ! Solaris, OpenIndiana, ...
             if (index(val, 'SunOS') > 0 .or. index(val, 'solaris') > 0) then
                 r = OS_SOLARIS
+                ret = r
                 return
             end if
 
             ! FreeBSD
             if (index(val, 'FreeBSD') > 0 .or. index(val, 'freebsd') > 0) then
                 r = OS_FREEBSD
+                ret = r
                 return
             end if
 
             ! OpenBSD
             if (index(val, 'OpenBSD') > 0 .or. index(val, 'openbsd') > 0) then
                 r = OS_OPENBSD
+                ret = r
                 return
             end if
         end if
@@ -103,6 +120,7 @@ integer function get_os_type() result(r)
 
         if (file_exists) then
             r = OS_LINUX
+            ret = r
             return
         end if
 
@@ -111,6 +129,7 @@ integer function get_os_type() result(r)
 
         if (file_exists) then
             r = OS_MACOS
+            ret = r
             return
         end if
 
@@ -119,6 +138,7 @@ integer function get_os_type() result(r)
 
         if (file_exists) then
             r = OS_FREEBSD
+            ret = r
             return
         end if
     end function get_os_type

From 670e273ebb70c7be3615af4649112d75f043246b Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Tue, 20 Jul 2021 00:13:31 -0300
Subject: [PATCH 09/10] Use join_path() in list_files()

---
 src/fpm_filesystem.F90 | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/src/fpm_filesystem.F90 b/src/fpm_filesystem.F90
index e5cfa9d982..b589c24415 100644
--- a/src/fpm_filesystem.F90
+++ b/src/fpm_filesystem.F90
@@ -351,11 +351,10 @@ end subroutine mkdir
 !!  - File/directory names return are relative to cwd, ie. preprended with `dir`
 !!  - Includes files starting with `.` except current directory and parent directory
 !!
-recursive subroutine list_files(dir, files, recurse, separator)
+recursive subroutine list_files(dir, files, recurse)
     character(len=*), intent(in) :: dir
     type(string_t), allocatable, intent(out) :: files(:)
     logical, intent(in), optional :: recurse
-    character(len=1), optional :: separator
 
     integer :: i
     type(string_t), allocatable :: dir_files(:)
@@ -368,18 +367,6 @@ recursive subroutine list_files(dir, files, recurse, separator)
     integer, parameter :: N_MAX = 256
     type(string_t) :: files_tmp(N_MAX)
     integer(kind=c_int) :: r
-    character(len=1) :: filesep
-
-    if (present(separator)) then
-        filesep = separator
-    else
-        select case (get_os_type())
-            case default
-                filesep = '/'
-            case (OS_WINDOWS)
-                filesep = '\'
-        end select
-    end if
 
     if (c_is_dir(dir(1:len_trim(dir))//c_null_char) .eq. 0) then
         allocate (files(0))
@@ -413,7 +400,7 @@ recursive subroutine list_files(dir, files, recurse, separator)
                 i = 1
             end if
 
-            files_tmp(i)%s = dir // filesep // string_fortran
+            files_tmp(i)%s = join_path(dir, string_fortran)
         end if
     end do
 
@@ -435,7 +422,7 @@ recursive subroutine list_files(dir, files, recurse, separator)
 
             do i=1,size(files)
                 if (c_is_dir(files(i)%s//c_null_char) .ne. 0) then
-                    call list_files(files(i)%s, dir_files, recurse=.true., separator=filesep)
+                    call list_files(files(i)%s, dir_files, recurse=.true.)
                     sub_dir_files = [sub_dir_files, dir_files]
                 end if
             end do

From bb0c412b4a331166c12f48b90dd0d5397da34e04 Mon Sep 17 00:00:00 2001
From: Carlos Une <brocolis@eml.cc>
Date: Tue, 20 Jul 2021 00:48:50 -0300
Subject: [PATCH 10/10] Cache `filesep` in `join_path` using the save attribute

---
 src/fpm_filesystem.F90 | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/fpm_filesystem.F90 b/src/fpm_filesystem.F90
index b589c24415..a26af75a6f 100644
--- a/src/fpm_filesystem.F90
+++ b/src/fpm_filesystem.F90
@@ -260,13 +260,23 @@ function join_path(a1,a2,a3,a4,a5) result(path)
     character(len=*), intent(in), optional :: a3, a4, a5
     character(len=:), allocatable          :: path
     character(len=1)                       :: filesep
+    logical, save                          :: has_cache = .false.
+    character(len=1), save                 :: cache = '/'
+    !$omp threadprivate(has_cache, cache)
 
-    select case (get_os_type())
-        case (OS_UNKNOWN, OS_LINUX, OS_MACOS, OS_CYGWIN, OS_SOLARIS, OS_FREEBSD, OS_OPENBSD)
-            filesep = '/'
-        case (OS_WINDOWS)
-            filesep = '\'
-    end select
+    if (has_cache) then
+        filesep = cache
+    else
+        select case (get_os_type())
+            case default
+                filesep = '/'
+            case (OS_WINDOWS)
+                filesep = '\'
+        end select
+
+        cache = filesep
+        has_cache = .true.
+    end if
 
     path = a1 // filesep // a2