tmpfile_windows: fix temp file name collisions when appending an extension
Formerly, tmpnam_s was used to ensure a unique file name, but then we'd
append an extension to it, invalidating its uniqueness. Instead, we now
do our own uniqueness check by attempting to create a unique empty file
for write with new names until it succeeds.
Bug: tint:812
Change-Id: I90b85074ad2281f9904f24e8fddda80d67e61ba7
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53061
Auto-Submit: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
diff --git a/src/utils/io/tmpfile_windows.cc b/src/utils/io/tmpfile_windows.cc
index 93634a8..a641d5f 100644
--- a/src/utils/io/tmpfile_windows.cc
+++ b/src/utils/io/tmpfile_windows.cc
@@ -22,17 +22,26 @@
namespace {
-std::string TmpFilePath() {
+std::string TmpFilePath(const std::string& ext) {
char name[L_tmpnam];
- if (tmpnam_s(name, L_tmpnam - 1) == 0) {
- return name;
+ // As we're adding an extension, to ensure the file is really unique, try
+ // creating it, failing if it already exists.
+ while (tmpnam_s(name, L_tmpnam - 1) == 0) {
+ std::string name_with_ext = std::string(name) + ext;
+ FILE* f = nullptr;
+ // The "x" arg forces the function to fail if the file already exists.
+ fopen_s(&f, name_with_ext.c_str(), "wbx");
+ if (f) {
+ fclose(f);
+ return name_with_ext;
+ }
}
- return "";
+ return {};
}
} // namespace
-TmpFile::TmpFile(std::string ext) : path_(TmpFilePath() + ext) {}
+TmpFile::TmpFile(std::string ext) : path_(TmpFilePath(ext)) {}
TmpFile::~TmpFile() {
if (!path_.empty()) {
