1 files changed, 50 insertions, 3 deletions
diff --git a/src/nvim/path.c b/src/nvim/path.c
index 12952f49db..f2339c8046 100644
--- a/src/nvim/path.c
+++ b/src/nvim/path.c
@@ -435,7 +435,7 @@ bool add_pathsep(char *p)
 /// @return [allocated] Copy of absolute path to `fname` or NULL when
 ///                     `fname` is NULL.
 char *FullName_save(const char *fname, bool force)
-  FUNC_ATTR_NONNULL_RET FUNC_ATTR_MALLOC
+  FUNC_ATTR_MALLOC
 {
   if (fname == NULL) {
     return NULL;
@@ -453,7 +453,7 @@ char *FullName_save(const char *fname, bool force)
 /// @param name An absolute or relative path.
 /// @return The absolute path of `name`.
 char_u *save_absolute_path(const char_u *name)
-  FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_RET FUNC_ATTR_NONNULL_ALL
+  FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   if (!path_is_absolute_path(name)) {
     return (char_u *)FullName_save((char *)name, true);
@@ -1715,7 +1715,7 @@ int vim_FullName(const char *fname, char *buf, size_t len, bool force)
 ///
 /// @param fname is the filename to expand
 /// @return [allocated] Full path (NULL for failure).
-char *fix_fname(char *fname)
+char *fix_fname(const char *fname)
 {
 #ifdef UNIX
   return FullName_save(fname, true);
@@ -2237,3 +2237,50 @@ int path_is_absolute_path(const char_u *fname)
   return *fname == '/' || *fname == '~';
 #endif
 }
+
+/// Builds a full path from an invocation name `argv0`, based on heuristics.
+///
+/// @param[in]  argv0     Name by which Nvim was invoked.
+/// @param[out] buf       Guessed full path to `argv0`.
+/// @param[in]  bufsize   Size of `buf`.
+///
+/// @see os_exepath
+void path_guess_exepath(const char *argv0, char *buf, size_t bufsize)
+  FUNC_ATTR_NONNULL_ALL
+{
+  char *path = getenv("PATH");
+
+  if (path == NULL || path_is_absolute_path((char_u *)argv0)) {
+    xstrlcpy(buf, argv0, bufsize);
+  } else if (argv0[0] == '.' || strchr(argv0, PATHSEP)) {
+    // Relative to CWD.
+    if (os_dirname((char_u *)buf, MAXPATHL) != OK) {
+      buf[0] = NUL;
+    }
+    xstrlcat(buf, PATHSEPSTR, bufsize);
+    xstrlcat(buf, argv0, bufsize);
+  } else {
+    // Search $PATH for plausible location.
+    const void *iter = NULL;
+    do {
+      const char *dir;
+      size_t dir_len;
+      iter = vim_env_iter(ENV_SEPCHAR, path, iter, &dir, &dir_len);
+      if (dir == NULL || dir_len == 0) {
+        break;
+      }
+      if (dir_len + 1 > sizeof(NameBuff)) {
+        continue;
+      }
+      xstrlcpy((char *)NameBuff, dir, dir_len + 1);
+      xstrlcat((char *)NameBuff, PATHSEPSTR, sizeof(NameBuff));
+      xstrlcat((char *)NameBuff, argv0, sizeof(NameBuff));
+      if (os_can_exe(NameBuff, NULL, false)) {
+        xstrlcpy(buf, (char *)NameBuff, bufsize);
+        return;
+      }
+    } while (iter != NULL);
+    // Not found in $PATH, fall back to argv0.
+    xstrlcpy(buf, argv0, bufsize);
+  }
+}