[llvm-bugs] [Bug 45307] New: temp_directory_path() returns path with trailing slash
via llvm-bugs
llvm-bugs at lists.llvm.org
Wed Mar 25 12:27:22 PDT 2020
https://bugs.llvm.org/show_bug.cgi?id=45307
Bug ID: 45307
Summary: temp_directory_path() returns path with trailing slash
Product: libc++
Version: unspecified
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: All Bugs
Assignee: unassignedclangbugs at nondot.org
Reporter: ldionne at apple.com
CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com
The following program works when run in an empty environment, but not when
TEMPDIR or some other temporary-directory-pointing environment variable is
defined:
$ cat <<EOF | clang++ -xc++ -std=c++17 - && ./a.out
#include <filesystem>
#include <iostream>
namespace fs = std::filesystem;
int main() {
fs::path tmp = fs::temp_directory_path();
fs::path p = tmp / "hello";
std::cout << "tmp = " << tmp << std::endl;
std::cout << "p.parent_path() = " << p.parent_path() << std::endl;
assert(p.parent_path() == tmp);
}
EOF
When run as `./a.out`, the program fails:
tmp = "/var/folders/10/r6bw68bs5b9gwjtrnl9dz0vm0000gn/T/"
p.parent_path() = "/var/folders/10/r6bw68bs5b9gwjtrnl9dz0vm0000gn/T"
Assertion failed: (p.parent_path() == tmp), function main, file <stdin>,
line 9.
Unsurprisingly, the environment contains the following entry:
TMPDIR=/var/folders/10/r6bw68bs5b9gwjtrnl9dz0vm0000gn/T/
When run as `env -i ./a.out`, the program succeeds and prints the following:
tmp = "/tmp"
p.parent_path() = "/tmp"
Comparison of paths is based on comparing the file-names exposed by begin()
through end(), and that is specified to yield an empty element at the end if
the path ends with a directory separator. So the comparison appears to be
behaving correctly.
However, I believe temp_directory_path() should normalize its return value and
not return a path with a trailing slash if the path it picks up from the
environment has a trailing slash. The reason is that the Standard says
(http://eel.is/c++draft/fs.op.temp.dir.path#5):
Example: For POSIX-based operating systems, an implementation might return
the path supplied by the first environment variable found in the list TMPDIR,
TMP, TEMP, TEMPDIR, or if none of these are found, "/tmp".
It seems weird that we'd return a path with a trailing slash when found in an
environment variable, but just "/tmp" without a trailing slash otherwise.
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