Perform some code maintenance

- Change IDT code so kprintf() isn't mandatory dependency
- Document current intentions around pthread_cancel()
- Make _npassert() an _unassert() in MODE=tiny

libc/assert.h

@@ -2,7 +2,6 @@
 #define COSMOPOLITAN_LIBC_ASSERT_H_
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
-#include "libc/intrin/kprintf.h"
 
 extern bool __assert_disable;
 void __assert_fail(const char *, const char *, int) hidden relegated;
@@ -24,13 +23,16 @@ void __assert_fail(const char *, const char *, int) hidden relegated;
     }                                \
   } while (0)
 
+#ifndef TINY
 #define _npassert(x)                 \
   do {                               \
     if (__builtin_expect(!(x), 0)) { \
-      kprintf("%s:%d: oh no!\n", __FILE__, __LINE__); \
       notpossible;                   \
     }                                \
   } while (0)
+#else
+#define _npassert(x) _unassert(x)
+#endif
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */

libc/intrin/extend.c

@@ -34,14 +34,11 @@ static void _mapframe(void *p, int f) {
   struct DirectMap dm;
   prot = PROT_READ | PROT_WRITE;
   flags = f | MAP_ANONYMOUS | MAP_FIXED;
-  if ((dm = sys_mmap(p, G, prot, flags, -1, 0)).addr != p) {
-    notpossible;
-  }
+  _npassert((dm = sys_mmap(p, G, prot, flags, -1, 0)).addr == p);
   __mmi_lock();
-  if (TrackMemoryInterval(&_mmi, (uintptr_t)p >> 16, (uintptr_t)p >> 16,
-                          dm.maphandle, prot, flags, false, false, 0, G)) {
-    notpossible;
-  }
+  _npassert(!TrackMemoryInterval(&_mmi, (uintptr_t)p >> 16, (uintptr_t)p >> 16,
+                                 dm.maphandle, prot, flags, false, false, 0,
+                                 G));
   __mmi_unlock();
 }
 
@@ -65,13 +62,11 @@ static void _mapframe(void *p, int f) {
  */
 noasan void *_extend(void *p, size_t n, void *e, int f, intptr_t h) {
   char *q;
-#ifndef NDEBUG
-  if ((uintptr_t)SHADOW(p) & (G - 1)) notpossible;
-  if ((uintptr_t)p + (G << kAsanScale) > h) notpossible;
-#endif
+  _npassert(!((uintptr_t)SHADOW(p) & (G - 1)));
+  _npassert((uintptr_t)p + (G << kAsanScale) <= h);
   for (q = e; q < ((char *)p + n); q += 8) {
     if (!((uintptr_t)q & (G - 1))) {
-      if (q + G > (char *)h) notpossible;
+      _npassert(q + G <= (char *)h);
       _mapframe(q, f);
       if (IsAsan()) {
         if (!((uintptr_t)SHADOW(q) & (G - 1))) {

libc/intrin/interrupts.S

@@ -52,7 +52,7 @@
 	.rept	30
 	push	%rsi			# preserve rsi
 	mov	$i,%sil			# rsi = exception number
-1:	jmp	1f			# 🦘
+1:	jmp	1f			# kangeroo
 	i = i - 1
 	.endr
 __excep1_isr:
@@ -71,7 +71,7 @@ __excep0_isr:
 	push	%rdx			# use to call kprintf
 	push	%r8
 	push	%r9
-	mov	48(%rsp),%rcx		# edx:rcx = "caller" cs:rip
+	mov	48(%rsp),%rcx		# edx:rcx = 'caller' cs:rip
 	mov	56(%rsp),%edx
 	mov	40(%rsp),%r8		# r8 = error code
 	mov	%cr2,%r9		# r9 = cr2, in case it is useful
@@ -91,10 +91,14 @@ __excep0_isr:
 	mov	%eax,%ds
 	mov	%eax,%es
 	ezlea	.excep_msg,di		# stack should be 16-byte aligned now
-	xor	%eax,%eax		# kprintf is variadic; remember to
+	xor	%eax,%eax		# kprintf is variadic, remember to
 					# pass no. of vector regs. used (= 0)
-	call	kprintf			# print error message
-	cli
+	.weak	kprintf			# weakly link kprintf() because this
+	ezlea	kprintf,bx		# module is a mandatory dependency
+	test	%ebx,%ebx		# and we want to keep life.com tiny
+	jz	8f
+	call	*%rbx			# print error message
+8:	cli
 9:	hlt
 	jmp	9b
 	/* TODO: link up with sigaction etc. */
@@ -105,7 +109,7 @@ __excep0_isr:
 isr_init:
 	testb	IsMetal()
 	jz	9f
-	ezlea	_tss+0x24,di		# fill up TSS; we already loaded
+	ezlea	_tss+0x24,di		# fill up TSS, we already loaded
 					# task register in ape/ape.S
 	ezlea	_isr_stk_1+ISR_STK_SZ,ax
 	and	$-ISR_STK_ALIGN,%al	# be paranoid & enforce correct

libc/intrin/memtrack.greg.c

@@ -49,7 +49,7 @@
 static void *MoveMemoryIntervals(struct MemoryInterval *d,
                                  const struct MemoryInterval *s, int n) {
   int i;
-  if (n < 0) unreachable;
+  _unassert(n >= 0);
   if (d > s) {
     for (i = n; i--;) {
       d[i] = s[i];
@@ -63,8 +63,8 @@ static void *MoveMemoryIntervals(struct MemoryInterval *d,
 }
 
 static void RemoveMemoryIntervals(struct MemoryIntervals *mm, int i, int n) {
-  if (i < 0) unreachable;
-  if (i + n > mm->i) unreachable;
+  _unassert(i >= 0);
+  _unassert(i + n <= mm->i);
   MoveMemoryIntervals(mm->p + i, mm->p + i + n, mm->i - (i + n));
   mm->i -= n;
 }
@@ -108,9 +108,9 @@ static bool ExtendMemoryIntervals(struct MemoryIntervals *mm) {
 }
 
 int CreateMemoryInterval(struct MemoryIntervals *mm, int i) {
-  if (i < 0) unreachable;
-  if (i > mm->i) unreachable;
-  if (mm->n < 0) unreachable;
+  _unassert(i >= 0);
+  _unassert(i <= mm->i);
+  _unassert(mm->n >= 0);
   if (UNLIKELY(mm->i == mm->n) && !ExtendMemoryIntervals(mm)) return enomem();
   MoveMemoryIntervals(mm->p + i + 1, mm->p + i, mm->i++ - i);
   return 0;
@@ -129,7 +129,7 @@ int ReleaseMemoryIntervals(struct MemoryIntervals *mm, int x, int y,
                            void wf(struct MemoryIntervals *, int, int)) {
   unsigned l, r;
   ASSERT_MEMTRACK();
-  if (y < x) unreachable;
+  _unassert(y >= x);
   if (!mm->i) return 0;
   // binary search for the lefthand side
   l = FindMemoryInterval(mm, x);
@@ -139,8 +139,8 @@ int ReleaseMemoryIntervals(struct MemoryIntervals *mm, int x, int y,
   // binary search for the righthand side
   r = FindMemoryInterval(mm, y);
   if (r == mm->i || (r > l && y < mm->p[r].x)) --r;
-  if (r < l) unreachable;
-  if (x > mm->p[r].y) unreachable;
+  _unassert(r >= l);
+  _unassert(x <= mm->p[r].y);
 
   // remove the middle of an existing map
   //
@@ -161,11 +161,11 @@ int ReleaseMemoryIntervals(struct MemoryIntervals *mm, int x, int y,
   // ----|mmmm|----------------- after
   //
   if (x > mm->p[l].x && x <= mm->p[l].y) {
-    if (y < mm->p[l].y) unreachable;
+    _unassert(y >= mm->p[l].y);
     if (IsWindows()) return einval();
     mm->p[l].size -= (size_t)(mm->p[l].y - (x - 1)) * FRAMESIZE;
     mm->p[l].y = x - 1;
-    if (mm->p[l].x > mm->p[l].y) unreachable;
+    _unassert(mm->p[l].x <= mm->p[l].y);
     ++l;
   }
 
@@ -176,11 +176,11 @@ int ReleaseMemoryIntervals(struct MemoryIntervals *mm, int x, int y,
   // ---------------|mm|-------- after
   //
   if (y >= mm->p[r].x && y < mm->p[r].y) {
-    if (x > mm->p[r].x) unreachable;
+    _unassert(x <= mm->p[r].x);
     if (IsWindows()) return einval();
     mm->p[r].size -= (size_t)((y + 1) - mm->p[r].x) * FRAMESIZE;
     mm->p[r].x = y + 1;
-    if (mm->p[r].x > mm->p[r].y) unreachable;
+    _unassert(mm->p[r].x <= mm->p[r].y);
     --r;
   }
 
@@ -198,7 +198,7 @@ int TrackMemoryInterval(struct MemoryIntervals *mm, int x, int y, long h,
                         long offset, long size) {
   unsigned i;
   ASSERT_MEMTRACK();
-  if (y < x) unreachable;
+  _unassert(y >= x);
   i = FindMemoryInterval(mm, x);
 
   // try to extend the righthand side of the lefthand entry

libc/thread/pthread_cancel.c

@@ -16,9 +16,52 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/errno.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/runtime/runtime.h"
 #include "libc/thread/thread.h"
 
+/**
+ * Cancels thread.
+ *
+ * This function currently isn't supported. In order to support this
+ * function we'd need to redesign the system call interface, and add
+ * bloat and complexity to every function that can return EINTR. You
+ * might want to consider using `nsync_note` instead, which provides
+ * much better cancellations because posix cancellations is a broken
+ * design. If you need to cancel i/o operations, try doing this:
+ *
+ *     _Thread_local bool gotusr1;
+ *     void OnUsr1(int sig) { gotusr1 = true; }
+ *     struct sigaction sa = {.sa_handler = OnUsr1};
+ *     sigaction(SIGUSR1, &sa, 0);
+ *     tkill(pthread_getunique_np(thread), SIGUSR1);
+ *
+ * The above code should successfully cancel a thread's blocking io
+ * operations in most cases, e.g.
+ *
+ *     void *MyThread(void *arg) {
+ *       sigset_t ss;
+ *       sigfillset(&ss);
+ *       sigdelset(&ss, SIGUSR1);
+ *       sigprocmask(SIG_SETMASK, &ss, 0);
+ *       while (!gotusr1) {
+ *         char buf[512];
+ *         ssize_t rc = read(0, buf, sizeof(buf));
+ *         if (rc == -1 && errno == EINTR) continue;
+ *         write(1, buf, rc);
+ *       }
+ *       return 0;
+ *     }
+ *
+ * This has the same correctness issue as glibc, but it's usually
+ * "good enough" if you only need cancellations to perform things
+ * like server shutdown and socket options like `SO_RCVTIMEO` can
+ * ensure it's even safer, since it can't possibly block forever.
+ *
+ * @see https://sourceware.org/bugzilla/show_bug.cgi?id=12683
+ */
 int pthread_cancel(pthread_t thread) {
-  return ESRCH;
+  kprintf("error: pthread_cancel() is unsupported, please read the "
+          "cosmopolitan libc documentation for further details\n");
+  _Exit(1);
 }

third_party/nsync/common.internal.h

@@ -222,11 +222,7 @@ static const uint32_t NSYNC_WAITER_TAG = 0x726d2ba9;
 
 #define CONTAINER(t_, f_, p_) ((t_ *)(((char *)(p_)) - offsetof(t_, f_)))
 
-#ifdef TINY
-#define ASSERT(x) _unassert(x)
-#else
 #define ASSERT(x) _npassert(x)
-#endif
 
 /* Return a pointer to the nsync_waiter_s containing nsync_dll_element_ *e. */
 #define DLL_NSYNC_WAITER(e)                 \

third_party/nsync/mu_semaphore.c

@@ -30,11 +30,7 @@ Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
 // clang-format off
 
-#ifdef TINY
-#define ASSERT(x) _unassert(x)
-#else
 #define ASSERT(x) _npassert(x)
-#endif
 
 /* Check that atomic operations on nsync_atomic_uint32_ can be applied to int. */
 static const int assert_int_size = 1 /