PR #1553: Adapt to syscall(2) removal in OpenBSD

Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/1553

OpenBSD will remove its generic syscall(2) interface, so setting the ABSL_HAVE_SYSCALL_WRITE define will result in a linking failure soon.

Make direct use of the write(2) syscall instead. OpenBSD's libc does not do any buffering for write, so there is no change of behavior.

A [variant of this patch][1] has been in use since early this year in OpenBSD's ports. There's no need to set ABSL_LOW_LEVEL_WRITE_SUPPORTED since that's already done a few lines up.

[1]: https://github.com/openbsd/ports/commit/5f9e56cd982c1f1fa5af867e56355091e1817786
Merge 0dcc88a3cdab513c598587d85423135e85cec330 into b841db22

Merging this change closes #1553

COPYBARA_INTEGRATE_REVIEW=https://github.com/abseil/abseil-cpp/pull/1553 from botovq:openbsd-syscall 0dcc88a3cdab513c598587d85423135e85cec330
PiperOrigin-RevId: 576552197
Change-Id: I13466703ddc9d50edf87da5d0c291aad642af49a

absl/base/internal/raw_logging.cc

@@ -56,8 +56,7 @@
 // ABSL_HAVE_SYSCALL_WRITE is defined when the platform provides the syscall
 //   syscall(SYS_write, /*int*/ fd, /*char* */ buf, /*size_t*/ len);
 // for low level operations that want to avoid libc.
-#if (defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__)) && \
-    !defined(__ANDROID__)
+#if (defined(__linux__) || defined(__FreeBSD__)) && !defined(__ANDROID__)
 #include <sys/syscall.h>
 #define ABSL_HAVE_SYSCALL_WRITE 1
 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
@@ -93,8 +92,7 @@ constexpr char kTruncated[] = " ... (message truncated)\n";
 bool VADoRawLog(char** buf, int* size, const char* format, va_list ap)
     ABSL_PRINTF_ATTRIBUTE(3, 0);
 bool VADoRawLog(char** buf, int* size, const char* format, va_list ap) {
-  if (*size < 0)
-    return false;
+  if (*size < 0) return false;
   int n = vsnprintf(*buf, static_cast<size_t>(*size), format, ap);
   bool result = true;
   if (n < 0 || n > *size) {
@@ -122,8 +120,7 @@ constexpr int kLogBufSize = 3000;
 bool DoRawLog(char** buf, int* size, const char* format, ...)
     ABSL_PRINTF_ATTRIBUTE(3, 4);
 bool DoRawLog(char** buf, int* size, const char* format, ...) {
-  if (*size < 0)
-    return false;
+  if (*size < 0) return false;
   va_list ap;
   va_start(ap, format);
   int n = vsnprintf(*buf, static_cast<size_t>(*size), format, ap);
@@ -242,8 +239,8 @@ void AsyncSignalSafeWriteError(const char* s, size_t len) {
   _write(/* stderr */ 2, s, static_cast<unsigned>(len));
 #else
   // stderr logging unsupported on this platform
-  (void) s;
-  (void) len;
+  (void)s;
+  (void)len;
 #endif
 }
 
@@ -258,7 +255,7 @@ void RawLog(absl::LogSeverity severity, const char* file, int line,
 bool RawLoggingFullySupported() {
 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
   return true;
-#else  // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
+#else   // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
   return false;
 #endif  // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
 }