Allow subprocess to use environ for environment

Typically allow subprocess to use `$PATH` to find binaries

Signed-off-by: Paul Guyot <pguyot@kallisys.net>

Author: pguyot

libs/eavmlib/src/atomvm.erl

@@ -347,14 +347,15 @@ get_creation() ->
 %% @param   Path    path to the command to execute
 %% @param   Args    arguments to pass to the command. First item is the name
 %%                  of the command
-%% @param   Envp    environment variables to pass to the command.
+%% @param   Envp    environment variables to pass to the command or `undefined'
+%%                  to use environ (VM environment variables)
 %% @param   Options options to run execve. Should be `[stdout]'
 %% @returns a tuple with the process id and a fd to the stdout of the process.
 %% @doc     Fork and execute a program using fork(2) and execve(2). Pipe stdout
 %%          so output of the program can be read with `atomvm:posix_read/2'.
 %% @end
 %%-----------------------------------------------------------------------------
--spec subprocess(Path :: iodata(), Args :: [iodata()], Env :: [iodata()], Options :: [stdout]) ->
+-spec subprocess(Path :: iodata(), Args :: [iodata()], Env :: [iodata()] | undefined, Options :: [stdout]) ->
     {ok, non_neg_integer(), posix_fd()} | {error, posix_error()}.
 subprocess(_Path, _Args, _Env, _Options) ->
     erlang:nif_error(undefined).

src/libAtomVM/posix_nifs.c

@@ -58,6 +58,10 @@
 #include "nifs.h"
 #include "posix_nifs.h"
 
+#if HAVE_EXECVE
+extern char **environ;
+#endif
+
 term posix_errno_to_term(int err, GlobalContext *glb)
 {
 #if HAVE_OPEN && HAVE_CLOSE || defined(HAVE_CLOCK_SETTIME) || defined(HAVE_SETTIMEOFDAY)
@@ -511,6 +515,9 @@ static term nif_atomvm_posix_select_stop(Context *ctx, int argc, term argv[])
 #if HAVE_EXECVE
 static void free_string_list(char **list)
 {
+    if (IS_NULL_PTR(list)) {
+        return;
+    }
     char **ptr = list;
     while (*ptr) {
         char *str = *ptr;
@@ -564,19 +571,26 @@ static term nif_atomvm_subprocess(Context *ctx, int argc, term argv[])
         free(path);
         RAISE_ERROR(BADARG_ATOM);
     }
-    char **envp = parse_string_list(argv[2]);
-    if (IS_NULL_PTR(envp)) {
-        free(path);
-        free_string_list(args);
-        RAISE_ERROR(BADARG_ATOM);
+    char **envp;
+    char **envp_array = NULL;
+    if (argv[2] == UNDEFINED_ATOM) {
+        envp = environ;
+    } else {
+        envp_array = parse_string_list(argv[2]);
+        if (IS_NULL_PTR(envp_array)) {
+            free(path);
+            free_string_list(args);
+            RAISE_ERROR(BADARG_ATOM);
+        }
+        envp = envp_array;
     }
 
     int pstdout[2];
     int r = pipe(pstdout);
     if (r < 0) {
         free(path);
         free_string_list(args);
-        free_string_list(envp);
+        free_string_list(envp_array);
         return errno_to_error_tuple_maybe_gc(ctx);
     }
     pid_t pid;
@@ -609,7 +623,7 @@ static term nif_atomvm_subprocess(Context *ctx, int argc, term argv[])
     if (UNLIKELY(r != 0)) {
         free(path);
         free_string_list(args);
-        free_string_list(envp);
+        free_string_list(envp_array);
         close(pstdout[0]);
         close(pstdout[1]);
         return error_tuple_maybe_gc(r, ctx);
@@ -620,7 +634,7 @@ static term nif_atomvm_subprocess(Context *ctx, int argc, term argv[])
         int err = errno;
         free(path);
         free_string_list(args);
-        free_string_list(envp);
+        free_string_list(envp_array);
         close(pstdout[0]);
         close(pstdout[1]);
         return error_tuple_maybe_gc(err, ctx);
@@ -646,7 +660,7 @@ static term nif_atomvm_subprocess(Context *ctx, int argc, term argv[])
     close(pstdout[1]); // close write-end of the pipe
     free(path);
     free_string_list(args);
-    free_string_list(envp);
+    free_string_list(envp_array);
 
     if (UNLIKELY(memory_ensure_free_opt(ctx, TUPLE_SIZE(3) + TERM_BOXED_RESOURCE_SIZE, MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
         RAISE_ERROR(OUT_OF_MEMORY_ATOM);

tests/libs/eavmlib/test_file.erl

@@ -322,7 +322,7 @@ test_subprocess(true) ->
     ok.
 
 test_subprocess_echo() ->
-    {ok, _Pid, StdoutFd} = atomvm:subprocess("/bin/echo", ["echo"], [], [stdout]),
+    {ok, _Pid, StdoutFd} = atomvm:subprocess("/bin/echo", ["echo"], undefined, [stdout]),
     {ok, <<"\n">>} = atomvm:posix_read(StdoutFd, 10),
     eof = atomvm:posix_read(StdoutFd, 10),
     ok = atomvm:posix_close(StdoutFd),