win32: rework adding of extensions to filenames

Previously there was one function to handle adding extensions to
executable filenames, add_win32_extension().  Refactor this into
three functions:

add_win32_extension() appends the suffix to the argument string
in-place.  The argument must be long enough to cope with this,
as is the case in ash where path_advance() adds 4 bytes to each
filename for just this reason.

alloc_win32_extension() is equivalent to the old add_win32_extension().
It allocates a string to hold the new filename then calls the new
add_win32_extension() function.  The caller is responsible for
managing the returned string.

auto_win32_extension() calls alloc_win32_extension() and saves the
resulting string using auto_string().  It's used where the new
filename is consumed immediately or the actual value isn't needed.

Rewrite code to use the most appropriate function.  Also reorder
some code in find_executable() and find_command().

6 files changed, 64 insertions, 98 deletions

diff --git a/debianutils/which.c b/debianutils/which.c
index 0b0a6a645..9b10b62f9 100644
--- a/debianutils/which.c
+++ b/debianutils/which.c
@@ -67,10 +67,9 @@ int which_main(int argc UNUSED_PARAM, char **argv)
                 /* If file contains a slash don't use PATH */
                 if (strchr(*argv, '/') || (ENABLE_PLATFORM_MINGW32 && strchr(*argv, '\\'))) {
 #if ENABLE_PLATFORM_MINGW32
-                        if ((p=add_win32_extension(*argv)) != NULL) {
+                        if ((p=auto_win32_extension(*argv)) != NULL) {
                                 missing = 0;
                                 puts(p);
-                                free(p);
                         }
                         else
 #endif
diff --git a/include/mingw.h b/include/mingw.h
index 025c4e22b..543172075 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -457,7 +457,16 @@ void init_winsock(void);
 int has_bat_suffix(const char *p);
 int has_exe_suffix(const char *p);
 int has_exe_suffix_or_dot(const char *name);
-char *add_win32_extension(const char *p);
+char *alloc_win32_extension(const char *p);
+int add_win32_extension(char *p);
+
+static inline char *auto_win32_extension(const char *p)
+{
+        extern char *auto_string(char *str) FAST_FUNC;
+        char *s = alloc_win32_extension(p);
+        return s ? auto_string(s) : NULL;
+}
+
 void FAST_FUNC convert_slashes(char *p);
 
 int err_win_to_posix(DWORD winerr);
diff --git a/libbb/executable.c b/libbb/executable.c
index aec829945..835341ed9 100644
--- a/libbb/executable.c
+++ b/libbb/executable.c
@@ -28,10 +28,6 @@ int FAST_FUNC file_is_executable(const char *name)
  * in all cases (*PATHp) contents are temporarily modified
  * but are restored on return (s/:/NUL/ and back).
  */
-#if !ENABLE_PLATFORM_MINGW32
-#define next_path_sep(s) strchr(s, ':')
-#endif
-
 char* FAST_FUNC find_executable(const char *filename, char **PATHp)
 {
         /* About empty components in $PATH:
@@ -44,38 +40,32 @@ char* FAST_FUNC find_executable(const char *filename, char **PATHp)
          */
         char *p, *n;
 #if ENABLE_PLATFORM_MINGW32
-        char *w;
+        char sep, *w;
 #endif
 
         p = *PATHp;
         while (p) {
                 int ex;
-#if ENABLE_PLATFORM_MINGW32
-                char sep;
 
-                n = (char*)next_path_sep(p);
-                if (n) {
-                        sep = *n;
-                        *n = '\0';
-                }
-#else
+#if !ENABLE_PLATFORM_MINGW32
                 n = strchr(p, ':');
                 if (n) *n = '\0';
+#else
+                n = (char*)next_path_sep(p);
+                if (n) { sep = *n; *n = '\0'; }
 #endif
                 p = concat_path_file(
                         p[0] ? p : ".", /* handle "::" case */
                         filename
                 );
-#if ENABLE_PLATFORM_MINGW32
-                if (n) *n++ = sep;
-#else
+#if !ENABLE_PLATFORM_MINGW32
                 if (n) *n++ = ':';
-#endif
-#if ENABLE_PLATFORM_MINGW32
-                if ((w=add_win32_extension(p))) {
-                        *PATHp = n;
+#else
+                if (n) *n++ = sep;
+                if ((w=alloc_win32_extension(p))) {
                         free(p);
-                        return w;
+                        p = w;
+                        /* following test will succeed */
                 }
 #endif
                 ex = file_is_executable(p);
diff --git a/shell/ash.c b/shell/ash.c
index cbe30a78b..587cf2abb 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -8405,7 +8405,7 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, c
 
 #if ENABLE_PLATFORM_MINGW32
         {
-                char *new_cmd = add_win32_extension(cmd);
+                char *new_cmd = alloc_win32_extension(cmd);
                 execve(new_cmd ? new_cmd : cmd, argv, envp);
                 free(new_cmd);
         }
@@ -8516,9 +8516,6 @@ printentry(struct tblentry *cmdp)
         int idx;
         const char *path;
         char *name;
-#if ENABLE_PLATFORM_MINGW32
-        char *n;
-#endif
 
         idx = cmdp->param.index;
         path = pathval();
@@ -8527,13 +8524,9 @@ printentry(struct tblentry *cmdp)
                 stunalloc(name);
         } while (--idx >= 0);
 #if ENABLE_PLATFORM_MINGW32
-        if ((n=add_win32_extension(name)) != NULL)
-                name = n;
+        add_win32_extension(name);
 #endif
         out1fmt("%s%s\n", name, (cmdp->rehash ? "*" : nullstr));
-#if ENABLE_PLATFORM_MINGW32
-        free(n);
-#endif
 }
 
 /*
@@ -8921,9 +8914,6 @@ describe_command(char *command, const char *path, int describe_command_verbose)
         case CMDNORMAL: {
                 int j = entry.u.index;
                 char *p;
-#if ENABLE_PLATFORM_MINGW32
-                char *q;
-#endif
                 if (j < 0) {
                         p = command;
                 } else {
@@ -8933,17 +8923,13 @@ describe_command(char *command, const char *path, int describe_command_verbose)
                         } while (--j >= 0);
                 }
 #if ENABLE_PLATFORM_MINGW32
-                if ((q=add_win32_extension(p)) != NULL)
-                        p = q;
+                add_win32_extension(p);
 #endif
                 if (describe_command_verbose) {
                         out1fmt(" is %s", p);
                 } else {
                         out1str(p);
                 }
-#if ENABLE_PLATFORM_MINGW32
-                free(q);
-#endif
                 break;
         }
 
@@ -13826,36 +13812,28 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path)
         struct tblentry *cmdp;
         int idx;
         int prev;
-        char *fullname IF_PLATFORM_MINGW32(= NULL);
+        char *fullname;
         struct stat statb;
         int e;
         int updatetbl;
         struct builtincmd *bcmd;
-#if ENABLE_PLATFORM_MINGW32
-        extern const char win_suffix[4][4];
-        int i, len;
-#endif
 
         /* If name contains a slash, don't use PATH or hash table */
         if (strchr(name, '/') || (ENABLE_PLATFORM_MINGW32 && strchr(name, '\\'))) {
                 entry->u.index = -1;
                 if (act & DO_ABS) {
 #if ENABLE_PLATFORM_MINGW32
-                        while ((fullname=add_win32_extension(name)) == NULL &&
-                                        stat(name, &statb) < 0 ) {
+                        if (auto_win32_extension(name) == NULL && stat(name, &statb) < 0) {
 #else
                         while (stat(name, &statb) < 0) {
-#endif
 #ifdef SYSV
                                 if (errno == EINTR)
                                         continue;
 #endif
+#endif
                                 entry->cmdtype = CMDUNKNOWN;
                                 return;
                         }
-#if ENABLE_PLATFORM_MINGW32
-                        free(fullname);
-#endif
                 }
                 entry->cmdtype = CMDNORMAL;
                 return;
@@ -13959,29 +13937,8 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path)
                         goto success;
                 }
 #if ENABLE_PLATFORM_MINGW32
-                /* first try appending suffixes (unless there's one already) */
-                i = 4;
-                len = strlen(fullname);
-                if (!has_exe_suffix_or_dot(fullname)) {
-                        /* path_advance() has reserved space for suffix */
-                        fullname[len] = '.';
-                        for (i=0; i<4; ++i) {
-                                memcpy(fullname+len+1, win_suffix[i], 4);
-                                if (stat(fullname, &statb) == 0)
-                                        break;
-                        }
-                }
-
-                if (i == 4) {
-                        /* adding a suffix failed (or wasn't tried), try original */
-                        fullname[len] = '\0';
-                        if (stat(fullname, &statb) < 0) {
-                                if (errno != ENOENT && errno != ENOTDIR)
-                                        e = errno;
-                                goto loop;
-                        }
-                }
-#else
+                add_win32_extension(fullname);
+#endif
                 while (stat(fullname, &statb) < 0) {
 #ifdef SYSV
                         if (errno == EINTR)
@@ -13991,7 +13948,6 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path)
                                 e = errno;
                         goto loop;
                 }
-#endif
                 e = EACCES;     /* if we fail, this will be the error */
                 if (!S_ISREG(statb.st_mode))
                         continue;
diff --git a/win32/mingw.c b/win32/mingw.c
index 707e6a3d2..08d955527 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1160,7 +1160,7 @@ int mingw_rmdir(const char *path)
         return rmdir(path);
 }
 
-const char win_suffix[4][4] = { "com", "exe", "bat", "cmd" };
+static const char win_suffix[4][4] = { "com", "exe", "bat", "cmd" };
 
 static int has_win_suffix(const char *name, int start)
 {
@@ -1191,33 +1191,45 @@ int has_exe_suffix_or_dot(const char *name)
         return last_char_is(name, '.') || has_win_suffix(name, 0);
 }
 
-/* check if path can be made into an executable by adding a suffix;
- * return an allocated string containing the path if it can;
- * return NULL if not.
+/* Check if path can be made into an executable by adding a suffix.
+ * The suffix is added to the end of the argument which must be
+ * long enough to allow this.
  *
- * if path already has a suffix don't even bother trying
+ * If the return value is TRUE the argument contains the new path,
+ * if FALSE the argument is unchanged.
  */
-char *add_win32_extension(const char *p)
+int add_win32_extension(char *p)
 {
-        char *path;
-        int i, len;
-
-        if (has_exe_suffix_or_dot(p)) {
-                return NULL;
+        if (!has_exe_suffix_or_dot(p)) {
+                int i, len = strlen(p);
+
+                p[len] = '.';
+                for (i=0; i<4; ++i) {
+                        memcpy(p+len+1, win_suffix[i], 4);
+                        if (file_is_executable(p))
+                                return TRUE;
+                }
+                p[len] = '\0';
         }
+        return FALSE;
+}
 
-        len = strlen(p);
-        path = xasprintf("%s.com", p);
+/* Check if path can be made into an executable by adding a suffix.
+ * Return an allocated string containing the path if it can;
+ * return NULL if not.
+ *
+ * If path already has a suffix don't even bother trying.
+ */
+char *alloc_win32_extension(const char *p)
+{
+        if (!has_exe_suffix_or_dot(p)) {
+                int len = strlen(p);
+                char *path = strcpy(xmalloc(len+5), p);
 
-        for (i=0; i<4; ++i) {
-                memcpy(path+len+1, win_suffix[i], 4);
-                if (file_is_executable(path)) {
+                if (add_win32_extension(path))
                         return path;
-                }
+                free(path);
         }
-
-        free(path);
-
         return NULL;
 }
 
diff --git a/win32/process.c b/win32/process.c
index e9b34b56d..b7f02e431 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -240,7 +240,7 @@ spawnveq(int mode, const char *path, char *const *argv, char *const *env)
                         p = strdup(new_argv[0]);
                 }
                 else {
-                        p = add_win32_extension(new_argv[0]);
+                        p = alloc_win32_extension(new_argv[0]);
                 }
 
                 if (p != NULL && has_bat_suffix(p)) {
@@ -307,7 +307,7 @@ mingw_spawn_interpreter(int mode, const char *prog, char *const *argv, char *con
         new_argv[nopts+1] = (char *)prog; /* pass absolute path */
         memcpy(new_argv+nopts+2, argv+1, sizeof(*argv)*argc);
 
-        if ((fullpath=add_win32_extension(interp.path)) != NULL ||
+        if ((fullpath=alloc_win32_extension(interp.path)) != NULL ||
                         file_is_executable(interp.path)) {
                 new_argv[0] = fullpath ? fullpath : interp.path;
                 ret = spawnveq(mode, new_argv[0], new_argv, envp);