Improve performance of printf functions

libc/runtime/ftraceinit.c

@@ -0,0 +1,56 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/runtime/runtime.h"
+#include "libc/str/str.h"
+
+/**
+ * Enables plaintext function tracing if `--ftrace` flag is passed.
+ *
+ * The `--ftrace` CLI arg is removed before main() is called. This code
+ * is intended for diagnostic purposes and assumes binaries are
+ * trustworthy and stack isn't corrupted. Logging plain text allows
+ * program structure to easily be visualized and hotspots identified w/
+ * `sed | sort | uniq -c | sort`. A compressed trace can be made by
+ * appending `--ftrace 2>&1 | gzip -4 >trace.gz` to the CLI arguments.
+ *
+ * @see libc/runtime/_init.S for documentation
+ */
+textstartup int ftrace_init(int argc, char *argv[]) {
+  int i;
+  bool foundflag;
+  foundflag = false;
+  for (i = 1; i <= argc; ++i) {
+    if (!foundflag) {
+      if (argv[i]) {
+        if (strcmp(argv[i], "--ftrace") == 0) {
+          foundflag = true;
+        } else if (strcmp(argv[i], "----ftrace") == 0) {
+          strcpy(argv[i], "--ftrace");
+        }
+      }
+    } else {
+      argv[i - 1] = argv[i];
+    }
+  }
+  if (foundflag) {
+    --argc;
+    ftrace_install();
+  }
+  return argc;
+}