Do better job documenting platform issues

README.md

@@ -200,23 +200,42 @@ gdb foo.com -ex 'add-symbol-file foo.com.dbg 0x401000'
 
 ### Linux
 
-Linux systems with WINE installed might have issues running APE programs
+Some Linux systems are configured to launch MZ executables under WINE.
-if WINE is registered with `binnfmt_misc`. To work around this, you need
+Other distros configure their stock installs so that APE programs will
-to remove WINE from `binfmt_misc`. You could also disable `binfmt_misc`
+print "run-detectors: unable to find an interpreter". For example:
-entirely.
 
+```sh
+jart@ubuntu:~$ wget https://cosmo.zip/pub/cosmos/bin/dash
+jart@ubuntu:~$ chmod +x dash
+jart@ubuntu:~$ ./dash
+run-detectors: unable to find an interpreter for ./dash
 ```
-sudo sh -c 'echo 0 > /proc/sys/fs/binfmt_misc/status'
+
+You can fix that by registering APE with `binfmt_misc`:
+
+```sh
+sudo wget -O /usr/bin/ape https://cosmo.zip/pub/cosmos/bin/ape-$(uname -m).elf
+sudo sh -c "echo ':APE:M::MZqFpD::/usr/bin/ape:' >/proc/sys/fs/binfmt_misc/register"
+sudo sh -c "echo ':APE-jart:M::jartsr::/usr/bin/ape:' >/proc/sys/fs/binfmt_misc/register"
+```
+
+You should be good now. APE will not only work, it'll launch executables
+400µs faster now too. However if things still didn't work out, it's also
+possible to disable `binfmt_misc` as follows:
+
+```sh
+sudo sh -c 'echo -1 > /proc/sys/fs/binfmt_misc/cli'     # remove Ubuntu's MZ interpreter
+sudo sh -c 'echo -1 > /proc/sys/fs/binfmt_misc/status'  # remove ALL binfmt_misc entries
 ```
 
 ### WSL
 
 It's normally unsafe to use APE in a WSL environment, because it tries
-to run them as WIN32 binaries within the WSL environment. In order to
+to run MZ executables as WIN32 binaries within the WSL environment. In
-make it safe to use Cosmopolitan software on WSL, you have to run:
+order to make it safe to use Cosmopolitan software on WSL, run this:
 
 ```sh
-sh -c "echo -1 > /proc/sys/fs/binfmt_misc/WSLInterop"
+sudo sh -c "echo -1 > /proc/sys/fs/binfmt_misc/WSLInterop"
 ```
 
 ## Discord Chatroom

libc/crt/crt.S

@@ -32,6 +32,15 @@ _apple:	mov	$_HOSTXNU,%cl
 	.endfn	_apple,weak,hidden
 #endif
 
+#if SupportsWindows() && defined(__x86_64__) && !IsTiny()
+//	implements all win32 apis on non-windows hosts
+//	it is just enough code to get a good backtrace
+__oops_win32:
+	ud2
+	nop
+	.endfn	__oops_win32
+#endif
+
 //	System Five userspace program entrypoint.
 //
 //	@param	rsp is [n,argv₀..argvₙ₋₁,0,envp₀..,0,auxv₀..,0,..]
@@ -76,7 +85,6 @@ _start:
 //	make win32 imps crash
 	.weak	ape_idata_iat
 	.weak	ape_idata_iatend
-	.weak	__oops_win32
 	ezlea	__oops_win32,ax
 	ezlea	ape_idata_iat,di
 	ezlea	ape_idata_iatend,cx

libc/runtime/winmain.greg.c

@@ -23,7 +23,6 @@
 #include "libc/intrin/nomultics.internal.h"
 #include "libc/intrin/weaken.h"
 #include "libc/limits.h"
-#include "libc/log/libfatal.internal.h"
 #include "libc/macros.internal.h"
 #include "libc/nexgen32e/rdtsc.h"
 #include "libc/nt/console.h"
@@ -45,7 +44,6 @@
 #include "libc/sock/internal.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/prot.h"
-
 #ifdef __x86_64__
 
 #define abi __msabi textwindows dontinstrument
@@ -55,6 +53,7 @@ __msabi extern typeof(CreateFileMapping) *const __imp_CreateFileMappingW;
 __msabi extern typeof(DuplicateHandle) *const __imp_DuplicateHandle;
 __msabi extern typeof(FreeEnvironmentStrings) *const __imp_FreeEnvironmentStringsW;
 __msabi extern typeof(GetConsoleMode) *const __imp_GetConsoleMode;
+__msabi extern typeof(GetCurrentDirectory) *const __imp_GetCurrentDirectoryW;
 __msabi extern typeof(GetCurrentProcessId) *const __imp_GetCurrentProcessId;
 __msabi extern typeof(GetEnvironmentStrings) *const __imp_GetEnvironmentStringsW;
 __msabi extern typeof(GetEnvironmentVariable) *const __imp_GetEnvironmentVariableW;
@@ -67,6 +66,7 @@ __msabi extern typeof(SetConsoleOutputCP) *const __imp_SetConsoleOutputCP;
 __msabi extern typeof(SetEnvironmentVariable) *const __imp_SetEnvironmentVariableW;
 __msabi extern typeof(SetStdHandle) *const __imp_SetStdHandle;
 __msabi extern typeof(VirtualProtect) *const __imp_VirtualProtect;
+__msabi extern typeof(WriteFile) *const __imp_WriteFile;
 // clang-format on
 
 void cosmo(int, char **, char **, long (*)[2]) wontreturn;
@@ -88,9 +88,33 @@ __funline char16_t *MyCommandLine(void) {
   return cmd;
 }
 
-// implements all win32 apis on non-windows hosts
+static abi char16_t *StrStr(const char16_t *haystack, const char16_t *needle) {
-static abi long __oops_win32(void) {
+  size_t i;
-  notpossible;
+  for (;;) {
+    for (i = 0;; ++i) {
+      if (!needle[i]) return (/*unconst*/ char16_t *)haystack;
+      if (!haystack[i]) break;
+      if (needle[i] != haystack[i]) break;
+    }
+    if (!*haystack++) break;
+  }
+  return 0;
+}
+
+static abi void PrintError(const char *s, size_t n) {
+#define PrintError(s) PrintError(s, sizeof(s) - 1)
+  __imp_WriteFile(__imp_GetStdHandle(kNtStdErrorHandle), s, n, 0, 0);
+}
+
+// detect the unholiest of environments
+static abi bool32 IsWslChimera(void) {
+  char16_t path[PATH_MAX];
+  return __imp_GetCurrentDirectoryW(PATH_MAX, path) &&  //
+         path[0] == '\\' &&                             //
+         path[1] == '\\' &&                             //
+         path[2] == 'w' &&                              //
+         path[3] == 's' &&                              //
+         path[4] == 'l';
 }
 
 // returns true if utf-8 path is a win32-style path that exists
@@ -239,12 +263,17 @@ abi int64_t WinMain(int64_t hInstance, int64_t hPrevInstance,
   extern char os asm("__hostos");
   os = _HOSTWINDOWS;  // madness https://news.ycombinator.com/item?id=21019722
   kStartTsc = rdtsc();
+  if (!IsTiny() && IsWslChimera()) {
+    PrintError("error: APE is running on WIN32 inside WSL. You need to run: "
+               "sudo sh -c 'echo -1 > /proc/sys/fs/binfmt_misc/WSLInterop'\n");
+    return 77 << 8;  // exit(77)
+  }
   __umask = 077;
   __pid = __imp_GetCurrentProcessId();
   cmdline = MyCommandLine();
 #ifdef SYSDEBUG
   // sloppy flag-only check for early initialization
-  if (__strstr16(cmdline, u"--strace")) ++__strace;
+  if (StrStr(cmdline, u"--strace")) ++__strace;
 #endif
   if (_weaken(WinSockInit)) {
     _weaken(WinSockInit)();

tool/cosmocc/README.md

@@ -93,14 +93,30 @@ If you use zsh and have trouble running APE programs try `sh -c ./prog`
 or simply upgrade to zsh 5.9+ (since we patched it two years ago). The
 same is the case for Python `subprocess`, old versions of fish, etc.
 
+If you're on Linux, then `binfmt_misc` might try to run APE programs
+under WINE, or say "run-detectors: unable to find an interpreter". You
+can fix that by running these commands:
+
+```sh
+sudo wget -O /usr/bin/ape https://cosmo.zip/pub/cosmos/bin/ape-$(uname -m).elf
+sudo sh -c "echo ':APE:M::MZqFpD::/usr/bin/ape:' >/proc/sys/fs/binfmt_misc/register"
+sudo sh -c "echo ':APE-jart:M::jartsr::/usr/bin/ape:' >/proc/sys/fs/binfmt_misc/register"
+```
+
 On Apple Silicon, `aarch64-unknown-cosmo-cc` produces ELF binaries. If
-you build a hello world program, then you need to say `ape ./hello` to
+you build a hello world program, then you need to say `ape ./hello`. If
-run it. Note this isn't an issue for `cosmocc` which will wrap the ELF
+you don't have an `ape` command then run `cc -o ape bin/ape-m1.c` which
-program in a shell script that'll compile your APE loader automatically
+should be moved to `/usr/local/bin/ape`. Your APE interpreter might
-as needed. This also isn't an issue if your login shell was built using
+already exist under a path like `$TMPDIR/.ape-1.9`. It's important to
-Cosmopolitan Libc, e.g. <https://cosmo.zip/pub/cosmos/bin/bash> because
+note this is only a gotcha for the cross compiler. Your `cosmocc`
-Cosmo's `execve()` implementation will seamlessly launch ELF files via
+compiler wraps the actual ELF binaries with a shell script that'll
-your APE Loader.
+extract and compile an APE loader automatically, as needed. This also
+isn't an issue if your login shell was built using Cosmopolitan Libc,
+e.g. <https://cosmo.zip/pub/cosmos/bin/bash>. That's because Cosmo's
+`execve()` implementation will automatically react to `ENOEXEC` from the
+kernel by re-launching the program under `/usr/local/bin/ape`. Lastly
+note that all other platforms that aren't Apple Arm64 use `/usr/bin/ape`
+as the hard-coded canonical interpreter path.
 
 On Windows, you need a shell in order to run the shell script wrappers
 from this toolchain. It's recommended that you download Cosmos binaries

tool/cosmocc/package.sh

@@ -122,9 +122,9 @@ cp -f o/x86_64/ape/ape-no-modify-self.o "$OUTDIR/x86_64-linux-cosmo/lib/"
 
 cp -f ape/ape-m1.c "$OUTDIR/bin/"
 cp -af tool/cosmocc/bin/* "$OUTDIR/bin/"
-cp -f o/x86_64/ape/ape.elf "$OUTDIR/bin/"
+cp -f o/x86_64/ape/ape.elf "$OUTDIR/bin/ape-x86_64.elf"
-cp -f o/x86_64/ape/ape.macho "$OUTDIR/bin/"
+cp -f o/x86_64/ape/ape.macho "$OUTDIR/bin/ape-x86_64.macho"
-cp -f o/aarch64/ape/ape.elf "$OUTDIR/bin/ape.aarch64"
+cp -f o/aarch64/ape/ape.elf "$OUTDIR/bin/ape-aarch64.elf"
 for x in assimilate march-native mktemper fixupobj zipcopy apelink pecheck mkdeps zipobj; do
   o//tool/build/apelink.com \
     -l o/x86_64/ape/ape.elf \