[libc-commits] [libc] [libc] implement localtime (PR #110363)

[Petr Hosek via libc-commits]

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In-Reply-To: <llvm.org/llvm/llvm-project/pull/110363 at github.com>


================
@@ -129,6 +154,28 @@ int64_t update_from_seconds(int64_t total_seconds, struct tm *tm) {
   if (years > INT_MAX || years < INT_MIN)
     return time_utils::out_of_range();
 
+  char timezone[TimeConstants::TIMEZONE_SIZE];
+  char *env_tz = getenv("TZ");
+  FILE *fp = NULL;
+  if (env_tz) {
+    strncpy(timezone, env_tz, sizeof(timezone));
+    timezone[sizeof(timezone) - 1] = '\0';
+  } else {
+    fp = fopen("/etc/timezone", "rb");
+    if (fp == NULL) {
+      return time_utils::out_of_range();
+    }
+
+    acquire_file(fp, timezone, TimeConstants::TIMEZONE_SIZE);
+  }
+
+  if (fp != NULL && file_usage == 0) {
+    release_file(fp, timezone);
+    return time_utils::out_of_range();
+  }
+
+  int offset = timezone::get_timezone_offset(timezone);
----------------
petrhosek wrote:

It's not about `open` vs `fopen`, on platforms like baremetal there's no filesystem at all, so any use file descriptors or I/O operations like `read` is a non-starter. This needs to be refactored so the common logic can be used across all platforms, and the filesystem bits should live in platforms specific implementation (e.g. `src/time/linux`). On platforms where filesystem is available, we should be using the internal API like `LIBC_NAMESPACE::openfile` rather than the POSIX API.

https://github.com/llvm/llvm-project/pull/110363