maint: port to macOS 11.2.3 (arm64)

* m4/gnulib-cache.m4: Add fopen-gnu, replacing cloexec and fopen.
Avoid getopt-posix-tests, since they are not needed for m4
and currently fail on macOS 11.2.3 (arm64).
* src/builtin.c (m4_incr, m4_decr): Avoid undefined behavior
on integer overflow that causes tests to fail on macOS.
* src/debug.c (debug_set_output):
* src/output.c (m4_tmpfile, m4_tmpopen):
* src/path.c (m4_fopen):
Use GNU fopen with "e" rather than set_cloexec_flag.  This is
simpler, and works around a Gnulib bug on macOS with fopen
being replaced by rpl_fopen sometimes but not other times.
* src/freeze.c (produce_frozen_state): Use GNU fopen with "e";
no need to expose the fd to subprocesses.

6 files changed, 21 insertions, 24 deletions

diff --git a/m4/gnulib-cache.m4 b/m4/gnulib-cache.m4
index 13c88156..5ba60b59 100644
--- a/m4/gnulib-cache.m4
+++ b/m4/gnulib-cache.m4
@@ -40,6 +40,7 @@
 #  --no-conditional-dependencies \
 #  --no-libtool \
 #  --macro-prefix=M4 \
+#  --avoid=getopt-posix-tests \
 #  --avoid=lock-tests \
 #  --avoid=tls-tests \
 #  announce-gen \
@@ -51,7 +52,6 @@
 #  c-ctype \
 #  c-stack \
 #  clean-temp \
-#  cloexec \
 #  close-stream \
 #  closein \
 #  config-h \
@@ -64,7 +64,7 @@
 #  fdl-1.3 \
 #  fflush \
 #  filenamecat \
-#  fopen \
+#  fopen-gnu \
 #  fopen-safer \
 #  fseeko \
 #  gendocs \
@@ -122,7 +122,6 @@ gl_MODULES([
   c-ctype
   c-stack
   clean-temp
-  cloexec
   close-stream
   closein
   config-h
@@ -135,7 +134,7 @@ gl_MODULES([
   fdl-1.3
   fflush
   filenamecat
-  fopen
+  fopen-gnu
   fopen-safer
   fseeko
   gendocs
@@ -182,7 +181,7 @@ gl_MODULES([
   xvasprintf-posix
 ])
 gl_WITH_CXX_TESTS
-gl_AVOID([lock-tests tls-tests])
+gl_AVOID([getopt-posix-tests lock-tests tls-tests])
 gl_SOURCE_BASE([lib])
 gl_M4_BASE([m4])
 gl_PO_BASE([])
diff --git a/src/builtin.c b/src/builtin.c
index 494b3c5a..38da0b4a 100644
--- a/src/builtin.c
+++ b/src/builtin.c
@@ -1155,7 +1155,12 @@ m4_incr (struct obstack *obs, int argc, token_data **argv)
   if (!numeric_arg (argv[0], ARG (1), &value))
     return;
 
-  shipout_int (obs, value + 1);
+  /* Minimize undefined C behavior on overflow.  This code assumes
+     that the implementation-defined overflow when casting unsigned to
+     signed is a silent twos-complement wrap-around.  */
+  uint32_t v = value;
+  int32_t w = v + 1;
+  shipout_int (obs, w);
 }
 
 static void
@@ -1169,7 +1174,12 @@ m4_decr (struct obstack *obs, int argc, token_data **argv)
   if (!numeric_arg (argv[0], ARG (1), &value))
     return;
 
-  shipout_int (obs, value - 1);
+  /* Minimize undefined C behavior on overflow.  This code assumes
+     that the implementation-defined overflow when casting unsigned to
+     signed is a silent twos-complement wrap-around.  */
+  uint32_t v = value;
+  int32_t w = v - 1;
+  shipout_int (obs, w);
 }
 
 /* This section contains the macros "divert", "undivert" and "divnum" for
diff --git a/src/debug.c b/src/debug.c
index 069d34d4..a5e3052c 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -210,13 +210,9 @@ debug_set_output (const char *name)
     debug_set_file (NULL);
   else
     {
-      fp = fopen (name, "a");
+      fp = fopen (name, "ae");
       if (fp == NULL)
         return false;
-
-      if (set_cloexec_flag (fileno (fp), true) != 0)
-        M4ERROR ((warning_status, errno,
-                  "Warning: cannot protect debug file across forks"));
       debug_set_file (fp);
     }
   return true;
diff --git a/src/freeze.c b/src/freeze.c
index 2a59a3aa..dca2e9cc 100644
--- a/src/freeze.c
+++ b/src/freeze.c
@@ -57,7 +57,7 @@ produce_frozen_state (const char *name)
   symbol *bucket;
   const builtin *bp;
 
-  file = fopen (name, O_BINARY ? "wb" : "w");
+  file = fopen (name, O_BINARY ? "wbe" : "we");
   if (!file)
     m4_failure (errno, "cannot open `%s'", name);
 
diff --git a/src/output.c b/src/output.c
index 361bb5b7..42d7386b 100644
--- a/src/output.c
+++ b/src/output.c
@@ -224,15 +224,12 @@ m4_tmpfile (int divnum)
     }
   name = m4_tmpname (divnum);
   register_temp_file (output_temp_dir, name);
-  file = fopen_temp (name, O_BINARY ? "wb+" : "w+", false);
+  file = fopen_temp (name, O_BINARY ? "wb+e" : "w+e", false);
   if (file == NULL)
     {
       unregister_temp_file (output_temp_dir, name);
       m4_failure (errno, "cannot create temporary file for diversion");
     }
-  else if (set_cloexec_flag (fileno (file), true) != 0)
-    M4ERROR ((warning_status, errno,
-              "Warning: cannot protect diversion across forks"));
   return file;
 }
 
@@ -263,11 +260,9 @@ m4_tmpopen (int divnum, bool reread)
     }
   name = m4_tmpname (divnum);
   /* We need update mode, to avoid truncation.  */
-  file = fopen_temp (name, O_BINARY ? "rb+" : "r+", false);
+  file = fopen_temp (name, O_BINARY ? "rb+e" : "r+e", false);
   if (file == NULL)
     m4_failure (errno, "cannot create temporary file for diversion");
-  else if (set_cloexec_flag (fileno (file), true) != 0)
-    m4_error (0, errno, _("cannot protect diversion across forks"));
   /* Update mode starts at the beginning of the stream, but sometimes
      we want the end.  */
   else if (!reread && fseeko (file, 0, SEEK_END) != 0)
diff --git a/src/path.c b/src/path.c
index f13f3289..b618c53d 100644
--- a/src/path.c
+++ b/src/path.c
@@ -110,7 +110,7 @@ add_include_directory (const char *dir)
 static FILE *
 m4_fopen (const char *file)
 {
-  FILE *fp = fopen (file, "r");
+  FILE *fp = fopen (file, "re");
   if (fp)
     {
       struct stat st;
@@ -121,9 +121,6 @@ m4_fopen (const char *file)
           errno = EISDIR;
           return NULL;
         }
-      if (set_cloexec_flag (fd, true) != 0)
-        M4ERROR ((warning_status, errno,
-                  "Warning: cannot protect input file across forks"));
     }
   return fp;
 }