Add Linux ptrace() tutorial

libc/stdio/append.internal.h

@@ -19,6 +19,8 @@ ssize_t appendw(char **, uint64_t);
 ssize_t appends(char **, const char *);
 ssize_t appendf(char **, const char *, ...);
 ssize_t vappendf(char **, const char *, va_list);
+ssize_t kappendf(char **, const char *, ...);
+ssize_t kvappendf(char **, const char *, va_list);
 
 #if defined(__GNUC__) && !defined(__STRICT_ANSI__)
 #define appendf(BUF, FMT, ...) appendf(BUF, PFLINK(FMT), ##__VA_ARGS__)

libc/stdio/fopen.c

@@ -56,21 +56,18 @@ static int openpathname(const char *pathname, int flags, bool *out_noclose) {
  * @note microsoft unilaterally deprecated this function lool
  */
 FILE *fopen(const char *pathname, const char *mode) {
-  FILE *f;
+  FILE *f = 0;
   bool noclose;
   int fd, flags;
-  STRACE("fopen(%s)", pathname);
   flags = fopenflags(mode);
   pathname = fixpathname(pathname, flags);
   if ((fd = openpathname(pathname, flags, &noclose)) != -1) {
     if ((f = fdopen(fd, mode)) != NULL) {
       f->noclose = noclose;
-      return f;
-    } else {
-      if (!noclose) close(fd);
-      return NULL;
+    } else if (!noclose) {
+      close(fd);
     }
-  } else {
-    return NULL;
   }
+  STRACE("fopen(%#s, %#s) → %p% m", pathname, mode, f);
+  return f;
 }

libc/stdio/kappendf.c

@@ -0,0 +1,40 @@
+/*-*- 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/stdio/append.internal.h"
+
+/**
+ * Appends formatted string to buffer w/ kprintf, e.g.
+ *
+ *     char *b = 0;
+ *     kappendf(&b, "hello %d\n", 123);
+ *     free(b);
+ *
+ * @return bytes appended or -1 if `ENOMEM`
+ * @see appendz(b).i to get buffer length
+ * @note O(1) amortized buffer growth
+ * @see kprintf()
+ */
+ssize_t kappendf(char **b, const char *fmt, ...) {
+  int n;
+  va_list va;
+  va_start(va, fmt);
+  n = kvappendf(b, fmt, va);
+  va_end(va);
+  return n;
+}

libc/stdio/kvappendf.c

@@ -0,0 +1,68 @@
+/*-*- 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/assert.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/macros.internal.h"
+#include "libc/mem/mem.h"
+#include "libc/stdio/append.internal.h"
+
+#define W sizeof(size_t)
+
+/**
+ * Appends formatted string to buffer.
+ *
+ * This is an alternative to vappendf() that uses the kprintf()
+ * formatting facility. This has some advantages in terms of
+ * performance, code size, and memory safety. There's also
+ * disadvantages, such as lack of floating-point directives.
+ *
+ * @see kprintf()
+ */
+ssize_t kvappendf(char **b, const char *f, va_list v) {
+  char *p;
+  int r, s;
+  size_t n;
+  va_list w;
+  struct appendz z;
+  z = appendz((p = *b));
+  va_copy(w, v);
+  if ((r = kvsnprintf(p + z.i, z.n ? z.n - W - z.i : 0, f, v)) >= 0) {
+    n = ROUNDUP(z.i + r + 1, 8) + W;
+    if (n > z.n) {
+      if (!z.n) z.n = W * 2;
+      while (n > z.n) z.n += z.n >> 1;
+      z.n = ROUNDUP(z.n, W);
+      if ((p = realloc(p, z.n))) {
+        z.n = malloc_usable_size(p);
+        assert(!(z.n & (W - 1)));
+        s = kvsnprintf(p + z.i, z.n - W - z.i, f, w);
+        assert(s == r);
+        *b = p;
+      } else {
+        va_end(w);
+        return -1;
+      }
+    }
+    z.i += r;
+    if (!IsTiny() && W == 8) z.i |= (size_t)APPEND_COOKIE << 48;
+    *(size_t *)(p + z.n - W) = z.i;
+  }
+  va_end(w);
+  return r;
+}

libc/stdio/tmpfile.c

@@ -18,7 +18,6 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/bits/safemacros.internal.h"
 #include "libc/calls/calls.h"
-#include "libc/calls/strace.internal.h"
 #include "libc/fmt/fmt.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/macros.internal.h"