Bring back gc() function

Renaming gc() to _gc() was a mistake since the better thing to do is put
it behind the _COSMO_SOURCE macro. We need this change because I haven't
wanted to use my amazing garbage collector ever since we renamed it. You
now need to define _COSMO_SOURCE yourself when using amalgamation header
and cosmocc users need to pass the -mcosmo flag to get the gc() function

Some other issues relating to cancelation have been fixed along the way.
We're also now putting cosmocc in a folder named `.cosmocc` so it can be
more safely excluded by grep --exclude-dir=.cosmocc --exclude-dir=o etc.

test/libc/calls/access_test.c

@@ -20,7 +20,7 @@
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/mem/alloca.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/sysv/consts/auxv.h"

test/libc/calls/cachestat_test.c

@@ -25,7 +25,7 @@
 #include "libc/errno.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/macros.internal.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/runtime/runtime.h"
 #include "libc/runtime/sysconf.h"
 #include "libc/stdio/rand.h"

test/libc/calls/copy_file_range_test.c

@@ -38,7 +38,7 @@ void SetUpOnce(void) {
 
 void Make(const char *path, int mode) {
   int fd, n = lemur64() & 0xfffff;
-  char *data = _gc(malloc(n));
+  char *data = gc(malloc(n));
   rngset(data, n, lemur64, -1);
   ASSERT_NE(-1, (fd = creat(path, mode)));
   ASSERT_SYS(0, n, write(fd, data, n));
@@ -77,8 +77,8 @@ TEST(copy_file_range, test) {
   size_t n, m;
   Make("foo", 0644);
   Copy("foo", "bar");
-  p = _gc(xslurp("foo", &n));
-  q = _gc(xslurp("bar", &m));
+  p = gc(xslurp("foo", &n));
+  q = gc(xslurp("bar", &m));
   ASSERT_EQ(n, m);
   ASSERT_EQ(0, memcmp(p, q, n));
 }

test/libc/calls/fchdir_test.c

@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/testlib/testlib.h"
 

test/libc/calls/ftruncate_test.c

@@ -23,7 +23,7 @@
 #include "libc/errno.h"
 #include "libc/intrin/safemacros.internal.h"
 #include "libc/limits.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/nexgen32e/vendor.internal.h"
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/stdio.h"

test/libc/calls/getcwd_test.c

@@ -22,7 +22,7 @@
 #include "libc/fmt/libgen.h"
 #include "libc/limits.h"
 #include "libc/macros.internal.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/serialize.h"
 #include "libc/str/str.h"
 #include "libc/testlib/testlib.h"

test/libc/calls/getrandom_test.c

@@ -22,7 +22,6 @@
 #include "libc/calls/struct/sigaction.h"
 #include "libc/calls/struct/sigset.h"
 #include "libc/errno.h"
-#include "libc/serialize.h"
 #include "libc/log/check.h"
 #include "libc/macros.internal.h"
 #include "libc/math.h"
@@ -30,6 +29,7 @@
 #include "libc/mem/mem.h"
 #include "libc/nexgen32e/x86feature.h"
 #include "libc/runtime/runtime.h"
+#include "libc/serialize.h"
 #include "libc/stdio/lcg.internal.h"
 #include "libc/stdio/rand.h"
 #include "libc/stdio/stdio.h"
@@ -70,7 +70,7 @@ void *TortureWorker(void *arg) {
 TEST(getrandom, test) {
   int i, n = 999;
   double e, w = 7.7;
-  char *buf = _gc(calloc(1, n));
+  char *buf = gc(calloc(1, n));
   ASSERT_SYS(0, 0, getrandom(0, 0, 0));
   ASSERT_SYS(0, n, getrandom(buf, n, 0));
   ASSERT_SYS(EFAULT, -1, getrandom(0, n, 0));
@@ -92,7 +92,7 @@ TEST(getrandom, test2) {
   double e, w = 7.7;
   struct sigaction sa;
   int i, k, m, n = 999;
-  char *buf = _gc(calloc(1, n));
+  char *buf = gc(calloc(1, n));
   sa.sa_flags = 0;
   sa.sa_handler = OnSig;
   sigemptyset(&sa.sa_mask);

test/libc/calls/ioctl_test.c

@@ -20,7 +20,7 @@
 #include "libc/calls/internal.h"
 #include "libc/log/check.h"
 #include "libc/log/log.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/sock/sock.h"

test/libc/calls/makedirs_test.c

@@ -19,7 +19,7 @@
 #include "libc/calls/calls.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/testlib/testlib.h"
 #include "libc/thread/thread.h"

test/libc/calls/mkdir_test.c

@@ -20,7 +20,7 @@
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/log/check.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/stdio.h"

test/libc/calls/mkntcmdline_test.c

@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/errno.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/proc/ntspawn.h"
 #include "libc/str/str.h"

test/libc/calls/mkntenvblock_test.c

@@ -16,7 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/proc/ntspawn.h"
 #include "libc/runtime/runtime.h"
 #include "libc/testlib/testlib.h"

test/libc/calls/mkntpath_test.c

@@ -19,7 +19,7 @@
 #include "libc/calls/internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/dce.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/testlib/testlib.h"
 #if SupportsWindows()
 

test/libc/calls/open_test.c

@@ -24,7 +24,7 @@
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/macros.internal.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"

test/libc/calls/openatemp_test.c

@@ -21,7 +21,7 @@
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/limits.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/at.h"

test/libc/calls/poll_test.c

@@ -96,7 +96,7 @@ TEST(poll, testNegativeOneFd_isIgnored) {
   EXPECT_SYS(0, 0, poll(fds, ARRAYLEN(fds), 1));
   EXPECT_STREQ("fd:-1 revents:<TODO:kPollNames>\n"
                "fd:3 revents:<TODO:kPollNames>\n",
-               _gc(FormatPollFd(&fds[0])));
+               gc(FormatPollFd(&fds[0])));
   ASSERT_SYS(0, 0, close(3));
 }
 

test/libc/calls/readlinkat_test.c

@@ -23,7 +23,7 @@
 #include "libc/limits.h"
 #include "libc/log/log.h"
 #include "libc/mem/gc.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/runtime/symbols.internal.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/at.h"

test/libc/calls/stackoverflow1_test.c

@@ -23,7 +23,7 @@
 #include "libc/dce.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/limits.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/runtime/sysconf.h"

test/libc/calls/stackoverflow2_test.c

@@ -22,7 +22,7 @@
 #include "libc/dce.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/limits.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/runtime/sysconf.h"

test/libc/calls/stackoverflow3_test.c

@@ -23,7 +23,7 @@
 #include "libc/calls/ucontext.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/limits.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/runtime/sysconf.h"

test/libc/calls/stackoverflow4_test.c

@@ -23,7 +23,7 @@
 #include "libc/calls/ucontext.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/limits.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/runtime/sysconf.h"

test/libc/calls/stat_test.c

@@ -25,7 +25,7 @@
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/limits.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/nt/files.h"
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/stdio.h"

test/libc/calls/writev_test.c

@@ -23,7 +23,7 @@
 #include "libc/limits.h"
 #include "libc/macros.internal.h"
 #include "libc/mem/gc.h"
-#include "libc/mem/gc.internal.h"
+#include "libc/mem/gc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/sock/sock.h"
@@ -55,7 +55,7 @@ TEST(writev, negative_einvalOrEfault) {
 TEST(writev, exceedsIovMax_einval) {
   if (IsWindows()) return;  // it's complicated
   int i, n = IOV_MAX + 1;
-  struct iovec *v = _gc(malloc(sizeof(struct iovec) * n));
+  struct iovec *v = gc(malloc(sizeof(struct iovec) * n));
   for (i = 0; i < n; ++i) {
     v[i].iov_base = "x";
     v[i].iov_len = 1;