which,ash: changes to which/command/type

Change how 'which' detects if it was run from a standalone shell:
the shell passes the undocumented '-s' option.  This is stricter
and more reliable than the previous method of checking the name
of the binary.

Add a function to determine the binary associated with a given
applet name.  This makes it possible for 'which' and 'command -v'
to list the correct binary even for applets other than 'busybox'.
For example, when the binary is called 'sh.exe' 'which sh' will
report its path.

In standalone shell mode 'command -V' and 'type' now report "xxx
is a builtin applet" rather than "xxx is xxx", which is true but
not very illuminating.

(GitHub issue #248)

4 files changed, 67 insertions, 23 deletions

diff --git a/debianutils/which.c b/debianutils/which.c
index 815ac71da..d00b92e0b 100644
--- a/debianutils/which.c
+++ b/debianutils/which.c
@@ -12,7 +12,12 @@
 //config:       which is used to find programs in your PATH and
 //config:       print out their pathnames.
 
-//applet:IF_WHICH(APPLET_NOFORK(which, which, BB_DIR_USR_BIN, BB_SUID_DROP, which))
+// NOTE: For WIN32 this applet is NOEXEC as alloc_system_drive() and
+//       find_executable() both allocate memory.  And find_executable()
+//       calls alloc_system_drive().
+
+//applet:IF_PLATFORM_MINGW32(IF_WHICH(APPLET_NOEXEC(which, which, BB_DIR_USR_BIN, BB_SUID_DROP, which)))
+//applet:IF_PLATFORM_POSIX(IF_WHICH(APPLET_NOFORK(which, which, BB_DIR_USR_BIN, BB_SUID_DROP, which)))
 
 //kbuild:lib-$(CONFIG_WHICH) += which.o
 
@@ -28,6 +33,13 @@
 
 #include "libbb.h"
 
+#if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
+enum {
+        OPT_a = (1 << 0),
+        OPT_s = (1 << 1)
+};
+#endif
+
 int which_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int which_main(int argc UNUSED_PARAM, char **argv)
 {
@@ -36,9 +48,7 @@ int which_main(int argc UNUSED_PARAM, char **argv)
         /* This sizeof(): bb_default_root_path is shorter than BB_PATH_ROOT_PATH */
         char buf[sizeof(BB_PATH_ROOT_PATH)];
 #if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
-        /* If we were run as 'which.exe' skip standalone shell behaviour */
-        int sh_standalone =
-                        is_suffixed_with_case(bb_busybox_exec_path, "which.exe") == NULL;
+        int sh_standalone;
 #endif
 
         env_path = getenv("PATH");
@@ -46,28 +56,25 @@ int which_main(int argc UNUSED_PARAM, char **argv)
                 /* env_path must be writable, and must not alloc, so... */
                 env_path = strcpy(buf, bb_default_root_path);
 
+#if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
+        /* '-s' option indicates we were run from a standalone shell */
+        getopt32(argv, "^" "as" "\0" "-1"/*at least one arg*/);
+        sh_standalone = option_mask32 & OPT_s;
+        option_mask32 &= ~OPT_s;
+#else
         getopt32(argv, "^" "a" "\0" "-1"/*at least one arg*/);
+#endif
         argv += optind;
 
         do {
                 int missing = 1;
 
 #if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
-                if (sh_standalone) {
-                        if (strcmp(*argv, "busybox") == 0 &&
-                                        is_prefixed_with_case(bb_basename(bb_busybox_exec_path),
-                                                                "busybox")) {
-                                missing = 0;
-                                puts(bb_busybox_exec_path);
-                                if (!option_mask32) /* -a not set */
-                                        break;
-                        }
-                        else if (find_applet_by_name(*argv) >= 0) {
-                                missing = 0;
-                                puts(*argv);
-                                if (!option_mask32) /* -a not set */
-                                        break;
-                        }
+                if (sh_standalone && find_applet_by_name(*argv) >= 0) {
+                        missing = 0;
+                        puts(applet_to_exe(*argv));
+                        if (!option_mask32) /* -a not set */
+                                break;
                 }
 #endif
 
@@ -87,15 +94,16 @@ int which_main(int argc UNUSED_PARAM, char **argv)
                                 puts(bs_to_slash(path));
                         }
 # if ENABLE_FEATURE_SH_STANDALONE
-                        else if (sh_standalone) {
+                        else if (sh_standalone && unix_path(*argv)) {
                                 const char *name = bb_basename(*argv);
 
-                                if (unix_path(*argv) && find_applet_by_name(name) >= 0) {
+                                if (find_applet_by_name(name) >= 0) {
                                         missing = 0;
                                         puts(name);
                                 }
                         }
 # endif
+                        free(path);
 #endif
                 } else {
                         char *path;
diff --git a/include/mingw.h b/include/mingw.h
index 8a9610898..5e01b874e 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -584,3 +584,4 @@ int unix_path(const char *path);
 int has_path(const char *file);
 int is_relative_path(const char *path);
 char *get_last_slash(const char *path);
+const char *applet_to_exe(const char *name);
diff --git a/shell/ash.c b/shell/ash.c
index afb865146..97075ed5f 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -8904,6 +8904,16 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, c
                                 (fs && fs->fpid == FS_SHELLEXEC)) {
                         /* mingw-w64's getopt() uses __argv[0] as the program name */
                         __argv[0] = (char *)cmd;
+                        /* 'which' wants to know if it was invoked from a standalone
+                         * shell.  Use the spare element of argv to add a flag, but
+                         * not if the first argument is '--help', that's a special
+                         * case. */
+                        if (strcmp(argv[0], "which") == 0 &&
+                                        (argv[1] == NULL || strcmp(argv[1], "--help") != 0)) {
+                                --argv;
+                                argv[0] = argv[1];
+                                argv[1] = (char *)"-s";
+                        }
 # else
                 if (APPLET_IS_NOEXEC(applet_no)) {
 # endif
@@ -9456,7 +9466,12 @@ describe_command(char *command, const char *path, int describe_command_verbose)
 #if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
                 if (j < -1) {
                         p = (char *)bb_basename(command);
-                        goto describe;
+                        if (describe_command_verbose) {
+                                out1fmt(" is a builtin applet");
+                        } else {
+                                out1str(applet_to_exe(p));
+                        }
+                        break;
                 }
 #endif
                 if (j < 0) {
@@ -9474,7 +9489,6 @@ describe_command(char *command, const char *path, int describe_command_verbose)
 #if ENABLE_PLATFORM_MINGW32
                 add_win32_extension(p);
                 bs_to_slash(p);
- IF_FEATURE_SH_STANDALONE(describe:)
 #endif
                 if (describe_command_verbose) {
                         out1fmt(" is %s", p);
diff --git a/win32/mingw.c b/win32/mingw.c
index 063a0c546..0fa2a1b8f 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -2130,3 +2130,24 @@ int is_relative_path(const char *path)
 {
         return !is_dir_sep(path[0]) && !has_dos_drive_prefix(path);
 }
+
+#if ENABLE_FEATURE_SH_STANDALONE
+/*
+ * In standalone shell mode it's possible there's no binary file
+ * corresponding to an applet name.  There's one case where it's
+ * easy to determine the corresponding binary:  if the applet name
+ * matches the file name from bb_busybox_exec_path (with appropriate
+ * allowance for 'busybox*.exe').
+ */
+const char *applet_to_exe(const char *name)
+{
+        const char *exefile = bb_basename(bb_busybox_exec_path);
+        const char *exesuff = is_prefixed_with_case(exefile, name);
+
+        if (exesuff && (strcmp(name, "busybox") == 0 ||
+                                                strcasecmp(exesuff, ".exe") == 0)) {
+                return bb_busybox_exec_path;
+        }
+        return name;
+}
+#endif