lib: fix -Wassign-enum warnings

configure --enable-debug now enables -Wassign-enum with clang,
identifying several enum "abuses" also fixed.

Reported-by: Gisle Vanem
Bug: https://github.com/curl/curl/commit/879007f8118771f4896334731aaca5850a154675#commitcomment-42087553

Closes #5929

15 files changed, 53 insertions, 48 deletions

diff --git a/docs/examples/sslbackend.c b/docs/examples/sslbackend.c
index 14c230390..12e515005 100644
--- a/docs/examples/sslbackend.c
+++ b/docs/examples/sslbackend.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -47,7 +47,7 @@ int main(int argc, char **argv)
     const curl_ssl_backend **list;
     int i;
 
-    result = curl_global_sslset(-1, NULL, &list);
+    result = curl_global_sslset((curl_sslbackend)-1, NULL, &list);
     assert(result == CURLSSLSET_UNKNOWN_BACKEND);
 
     for(i = 0; list[i]; i++)
@@ -62,7 +62,7 @@ int main(int argc, char **argv)
     result = curl_global_sslset((curl_sslbackend)id, NULL, NULL);
   }
   else
-    result = curl_global_sslset(-1, name, NULL);
+    result = curl_global_sslset((curl_sslbackend)-1, name, NULL);
 
   if(result == CURLSSLSET_UNKNOWN_BACKEND) {
     fprintf(stderr, "Unknown SSL backend id: %s\n", name);
diff --git a/lib/easyoptions.c b/lib/easyoptions.c
index 9145ba7fc..0ab6a3fc6 100644
--- a/lib/easyoptions.c
+++ b/lib/easyoptions.c
@@ -332,7 +332,7 @@ struct curl_easyoption Curl_easyopts[] = {
   {"XFERINFODATA", CURLOPT_XFERINFODATA, CURLOT_CBPTR, 0},
   {"XFERINFOFUNCTION", CURLOPT_XFERINFOFUNCTION, CURLOT_FUNCTION, 0},
   {"XOAUTH2_BEARER", CURLOPT_XOAUTH2_BEARER, CURLOT_STRING, 0},
-  {NULL, 0, 0, 0} /* end of table */
+  {NULL, CURLOPT_LASTENTRY, 0, 0} /* end of table */
 };
 
 #ifdef DEBUGBUILD
diff --git a/lib/optiontable.pl b/lib/optiontable.pl
index ce5d02015..9c3b62619 100644
--- a/lib/optiontable.pl
+++ b/lib/optiontable.pl
@@ -101,7 +101,7 @@ for my $name (sort @names) {
 }
 
 print <<FOOT
-  {NULL, 0, 0, 0} /* end of table */
+  {NULL, CURLOPT_LASTENTRY, 0, 0} /* end of table */
 };
 
 #ifdef DEBUGBUILD
diff --git a/lib/security.c b/lib/security.c
index fbfa70741..89443af53 100644
--- a/lib/security.c
+++ b/lib/security.c
@@ -7,10 +7,10 @@
  * rewrite to work around the paragraph 2 in the BSD licenses as explained
  * below.
  *
- * Copyright (c) 1998, 1999, 2017 Kungliga Tekniska Högskolan
+ * Copyright (c) 1998, 1999 Kungliga Tekniska Högskolan
  * (Royal Institute of Technology, Stockholm, Sweden).
  *
- * Copyright (C) 2001 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 2001 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * All rights reserved.
  *
@@ -529,7 +529,7 @@ static CURLcode choose_mech(struct connectdata *conn)
   if(ret != AUTH_CONTINUE) {
     if(ret != AUTH_OK) {
       /* Mechanism has dumped the error to stderr, don't error here. */
-      return -1;
+      return CURLE_USE_SSL_FAILED;
     }
     DEBUGASSERT(ret == AUTH_OK);
 
diff --git a/lib/vtls/gtls.c b/lib/vtls/gtls.c
index 9f280447c..978c61abf 100644
--- a/lib/vtls/gtls.c
+++ b/lib/vtls/gtls.c
@@ -304,7 +304,7 @@ static gnutls_x509_crt_fmt_t do_file_type(const char *type)
     return GNUTLS_X509_FMT_PEM;
   if(strcasecompare(type, "DER"))
     return GNUTLS_X509_FMT_DER;
-  return -1;
+  return GNUTLS_X509_FMT_PEM; /* default to PEM */
 }
 
 #define GNUTLS_CIPHERS "NORMAL:-ARCFOUR-128:-CTYPE-ALL:+CTYPE-X509"
diff --git a/lib/vtls/nss.c b/lib/vtls/nss.c
index 8e9de3cd6..25098814a 100644
--- a/lib/vtls/nss.c
+++ b/lib/vtls/nss.c
@@ -1672,7 +1672,8 @@ static CURLcode nss_load_ca_certificates(struct connectdata *conn,
       if(!dir)
         return CURLE_SSL_CACERT_BADFILE;
 
-      while((entry = PR_ReadDir(dir, PR_SKIP_BOTH | PR_SKIP_HIDDEN))) {
+      while((entry =
+             PR_ReadDir(dir, (PRDirFlags)(PR_SKIP_BOTH | PR_SKIP_HIDDEN)))) {
         char *fullpath = aprintf("%s/%s", capath, entry->name);
         if(!fullpath) {
           PR_CloseDir(dir);
diff --git a/m4/curl-compilers.m4 b/m4/curl-compilers.m4
index b0d5d4213..7d59f0667 100644
--- a/m4/curl-compilers.m4
+++ b/m4/curl-compilers.m4
@@ -945,6 +945,10 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
               tmp_CFLAGS="$tmp_CFLAGS -Wno-varargs"
             fi
           fi
+          dnl clang 7 or later
+          if test "$compiler_num" -ge "700"; then
+            CURL_ADD_COMPILER_WARNINGS([tmp_CFLAGS], [assign-enum])
+          fi
         fi
         ;;
         #
diff --git a/tests/libtest/lib1538.c b/tests/libtest/lib1538.c
index 91481e88d..0f91e2f0c 100644
--- a/tests/libtest/lib1538.c
+++ b/tests/libtest/lib1538.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -31,12 +31,12 @@ int test(char *URL)
   CURLSHcode shareret;
   (void)URL;
 
-  curl_easy_strerror(INT_MAX);
-  curl_multi_strerror(INT_MAX);
-  curl_share_strerror(INT_MAX);
-  curl_easy_strerror(-INT_MAX);
-  curl_multi_strerror(-INT_MAX);
-  curl_share_strerror(-INT_MAX);
+  curl_easy_strerror((CURLcode)INT_MAX);
+  curl_multi_strerror((CURLMcode)INT_MAX);
+  curl_share_strerror((CURLSHcode)INT_MAX);
+  curl_easy_strerror((CURLcode)-INT_MAX);
+  curl_multi_strerror((CURLMcode)-INT_MAX);
+  curl_share_strerror((CURLSHcode)-INT_MAX);
   for(easyret = CURLE_OK; easyret <= CURL_LAST; easyret++) {
     printf("e%d: %s\n", (int)easyret, curl_easy_strerror(easyret));
   }
diff --git a/tests/libtest/lib1560.c b/tests/libtest/lib1560.c
index 20f852310..cc61199e9 100644
--- a/tests/libtest/lib1560.c
+++ b/tests/libtest/lib1560.c
@@ -638,7 +638,7 @@ static CURLUPart part2id(char *part)
     return CURLUPART_FRAGMENT;
   if(!strcmp("zoneid", part))
     return CURLUPART_ZONEID;
-  return 9999; /* bad input => bad output */
+  return (CURLUPart)9999; /* bad input => bad output */
 }
 
 static CURLUcode updateurl(CURLU *u, const char *cmd, unsigned int setflags)
diff --git a/tests/libtest/lib1592.c b/tests/libtest/lib1592.c
index 5e6bf04eb..ce0892be2 100644
--- a/tests/libtest/lib1592.c
+++ b/tests/libtest/lib1592.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -43,7 +43,7 @@ int test(char *URL)
   int stillRunning;
   CURLM *multiHandle = NULL;
   CURL *curl = NULL;
-  CURLMcode res = CURLM_OK;
+  CURLcode res = CURLE_OK;
   int timeout;
 
   global_init(CURL_GLOBAL_ALL);
diff --git a/tests/libtest/lib556.c b/tests/libtest/lib556.c
index 0595000ce..82e8b71dc 100644
--- a/tests/libtest/lib556.c
+++ b/tests/libtest/lib556.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -96,7 +96,7 @@ int test(char *URL)
     }
 
     if(iolen != 0)
-      res = TEST_ERR_FAILURE;
+      res = (CURLcode)TEST_ERR_FAILURE;
   }
 
 test_cleanup:
diff --git a/tests/libtest/lib583.c b/tests/libtest/lib583.c
index 86dd8b55a..3e2fe3867 100644
--- a/tests/libtest/lib583.c
+++ b/tests/libtest/lib583.c
@@ -35,7 +35,7 @@ int test(char *URL)
   int stillRunning;
   CURLM *multiHandle = NULL;
   CURL *curl = NULL;
-  CURLMcode res = CURLM_OK;
+  CURLcode res = CURLE_OK;
 
   global_init(CURL_GLOBAL_ALL);
 
diff --git a/tests/libtest/lib661.c b/tests/libtest/lib661.c
index a4f2c8e5c..454d8f337 100644
--- a/tests/libtest/lib661.c
+++ b/tests/libtest/lib661.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
diff --git a/tests/libtest/mk-lib1521.pl b/tests/libtest/mk-lib1521.pl
index e71fe1e51..9b57b64ee 100755
--- a/tests/libtest/mk-lib1521.pl
+++ b/tests/libtest/mk-lib1521.pl
@@ -297,7 +297,7 @@ while(<STDIN>) {
 
 
 print <<FOOTER
-  curl_easy_setopt(curl, 1, 0);
+  curl_easy_setopt(curl, (CURLoption)1, 0);
   res = CURLE_OK;
 test_cleanup:
   curl_easy_cleanup(curl);
diff --git a/tests/libtest/test.h b/tests/libtest/test.h
index 4806375a0..3e92598bc 100644
--- a/tests/libtest/test.h
+++ b/tests/libtest/test.h
@@ -86,18 +86,18 @@ extern int unitfail;
 ** For portability reasons TEST_ERR_* values should be less than 127.
 */
 
-#define TEST_ERR_MAJOR_BAD     126
-#define TEST_ERR_RUNS_FOREVER  125
-#define TEST_ERR_EASY_INIT     124
-#define TEST_ERR_MULTI_INIT    123
-#define TEST_ERR_NUM_HANDLES   122
-#define TEST_ERR_SELECT        121
-#define TEST_ERR_SUCCESS       120
-#define TEST_ERR_FAILURE       119
-#define TEST_ERR_USAGE         118
-#define TEST_ERR_FOPEN         117
-#define TEST_ERR_FSTAT         116
-#define TEST_ERR_BAD_TIMEOUT   115
+#define TEST_ERR_MAJOR_BAD     (CURLcode) 126
+#define TEST_ERR_RUNS_FOREVER  (CURLcode) 125
+#define TEST_ERR_EASY_INIT     (CURLcode) 124
+#define TEST_ERR_MULTI         (CURLcode) 123
+#define TEST_ERR_NUM_HANDLES   (CURLcode) 122
+#define TEST_ERR_SELECT        (CURLcode) 121
+#define TEST_ERR_SUCCESS       (CURLcode) 120
+#define TEST_ERR_FAILURE       (CURLcode) 119
+#define TEST_ERR_USAGE         (CURLcode) 118
+#define TEST_ERR_FOPEN         (CURLcode) 117
+#define TEST_ERR_FSTAT         (CURLcode) 116
+#define TEST_ERR_BAD_TIMEOUT   (CURLcode) 115
 
 /*
 ** Macros for test source code readability/maintainability.
@@ -154,7 +154,7 @@ extern int unitfail;
 #define exe_multi_init(A,Y,Z) do {                                 \
   if(((A) = curl_multi_init()) == NULL) {                          \
     fprintf(stderr, "%s:%d curl_multi_init() failed\n", (Y), (Z)); \
-    res = TEST_ERR_MULTI_INIT;                                     \
+    res = TEST_ERR_MULTI;                                          \
   }                                                                \
 } while(0)
 
@@ -178,7 +178,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_easy_setopt() failed, "    \
             "with code %d (%s)\n",                         \
             (Y), (Z), (int)ec, curl_easy_strerror(ec));    \
-    res = (int)ec;                                         \
+    res = ec;                                              \
   }                                                        \
 } while(0)
 
@@ -202,7 +202,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_setopt() failed, "    \
             "with code %d (%s)\n",                          \
             (Y), (Z), (int)ec, curl_multi_strerror(ec));    \
-    res = (int)ec;                                          \
+    res = TEST_ERR_MULTI;                                   \
   }                                                         \
 } while(0)
 
@@ -226,7 +226,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_add_handle() failed, " \
             "with code %d (%s)\n",                           \
             (Y), (Z), (int)ec, curl_multi_strerror(ec));     \
-    res = (int)ec;                                           \
+    res = TEST_ERR_MULTI;                                    \
   }                                                          \
 } while(0)
 
@@ -250,7 +250,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_remove_handle() failed, " \
             "with code %d (%s)\n",                              \
             (Y), (Z), (int)ec, curl_multi_strerror(ec));        \
-    res = (int)ec;                                              \
+    res = TEST_ERR_MULTI;                                       \
   }                                                             \
 } while(0)
 
@@ -275,7 +275,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_perform() failed, "        \
             "with code %d (%s)\n",                               \
             (Y), (Z), (int)ec, curl_multi_strerror(ec));         \
-    res = (int)ec;                                               \
+    res = TEST_ERR_MULTI;                                        \
   }                                                              \
   else if(*((B)) < 0) {                                          \
     fprintf(stderr, "%s:%d curl_multi_perform() succeeded, "     \
@@ -305,7 +305,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_fdset() failed, "              \
             "with code %d (%s)\n",                                   \
             (Y), (Z), (int)ec, curl_multi_strerror(ec));             \
-    res = (int)ec;                                                   \
+    res = TEST_ERR_MULTI;                                            \
   }                                                                  \
   else if(*((E)) < -1) {                                             \
     fprintf(stderr, "%s:%d curl_multi_fdset() succeeded, "           \
@@ -335,7 +335,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_timeout() failed, "    \
             "with code %d (%s)\n",                           \
             (Y), (Z), (int)ec, curl_multi_strerror(ec));     \
-    res = (int)ec;                                           \
+    res = TEST_ERR_BAD_TIMEOUT;                              \
   }                                                          \
   else if(*((B)) < -1L) {                                    \
     fprintf(stderr, "%s:%d curl_multi_timeout() succeeded, " \
@@ -365,7 +365,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_poll() failed, "              \
             "with code %d (%s)\n",                                  \
             (Y), (Z), (int)ec, curl_multi_strerror(ec));            \
-    res = (int)ec;                                                  \
+    res = TEST_ERR_MULTI;                                           \
   }                                                                 \
   else if(*((E)) < 0) {                                             \
     fprintf(stderr, "%s:%d curl_multi_poll() succeeded, "           \
@@ -395,7 +395,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_multi_wakeup() failed, " \
             "with code %d (%s)\n",                       \
             (Y), (Z), (int)ec, curl_multi_strerror(ec)); \
-    res = (int)ec;                                       \
+    res = TEST_ERR_MULTI;                                \
   }                                                      \
 } while(0)
 
@@ -470,7 +470,7 @@ extern int unitfail;
     fprintf(stderr, "%s:%d curl_global_init() failed, " \
             "with code %d (%s)\n",                      \
             (Y), (Z), (int)ec, curl_easy_strerror(ec)); \
-    res = (int)ec;                                      \
+    res = ec;                                           \
   }                                                     \
 } while(0)