BR 3392535: warning on redefine, promote define-on-pass2 to error

If we redefine consistently, make it a suppressed-by-default warning.
If we end up doing the define on pass 2, promote that to a
default-error warning; using a default-error warning allows the user
to demote it should they so wish.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Requested-by: C. Masloch <pushbx@38.de>

3 files changed, 37 insertions, 26 deletions

diff --git a/asm/error.c b/asm/error.c
index 61c89740..f6098f4c 100644
--- a/asm/error.c
+++ b/asm/error.c
@@ -74,6 +74,8 @@ const struct warning warnings[WARN_ALL+1] = {
     {"unknown-warning", "unknown warning in -W/-w or warning directive", off},
     {"negative-rep", "regative %rep count", on},
     {"phase", "phase error during stabilization", off},
+    {"label-redef", "label redefined to an identical value", off},
+    {"label-redef-late", "label (re)defined during code generation", err},
 
     /* THESE ENTRIES SHOULD COME LAST */
     {"other", "any warning not specifially mentioned above", on},
diff --git a/asm/labels.c b/asm/labels.c
index a073f798..d0904ad3 100644
--- a/asm/labels.c
+++ b/asm/labels.c
@@ -494,35 +494,43 @@ void define_label(const char *label, int32_t segment,
         lptr->defn.size != size;
     global_offset_changed += changed;
 
-    if (changed) {
-        if (lastdef == lpass) {
-            int32_t saved_line = 0;
-            const char *saved_fname = NULL;
-
-            /*
-             * Defined elsewhere in the program, seen in this pass.
-             */
+    if (lastdef == lpass) {
+        int32_t saved_line = 0;
+        const char *saved_fname = NULL;
+        int noteflags;
+
+        /*
+         * Defined elsewhere in the program, seen in this pass.
+         */
+        if (changed) {
             nasm_error(ERR_NONFATAL,
                        "label `%s' inconsistently redefined",
                        lptr->defn.label);
-
-            src_get(&saved_line, &saved_fname);
-            src_set(lptr->defn.def_line, lptr->defn.def_file);
-            nasm_error(ERR_NOTE, "label `%s' originally defined here",
+            noteflags = ERR_NOTE;
+        } else {
+            nasm_error(ERR_WARNING|WARN_LABEL_REDEF|ERR_PASS2,
+                       "label `%s' redefined to an identical value",
                        lptr->defn.label);
-            src_set(saved_line, saved_fname);
-        } else if (pass0 > 1 && lptr->defn.type != LBL_SPECIAL) {
-            /*
-             * This probably should be ERR_NONFATAL, but not quite yet.  As a
-             * special case, LBL_SPECIAL symbols are allowed to be changed
-             * even during the last pass.
-             */
-            nasm_error(ERR_WARNING, "label `%s' %s during code generation",
-                       lptr->defn.label,
-                       created ? "defined" : "changed");
+            noteflags = ERR_NOTE|WARN_LABEL_REDEF|ERR_PASS2;
         }
-    }
 
+        src_get(&saved_line, &saved_fname);
+        src_set(lptr->defn.def_line, lptr->defn.def_file);
+        nasm_error(noteflags, "label `%s' originally defined here", lptr->defn.label);
+        src_set(saved_line, saved_fname);
+    } else if (changed && pass0 > 1 && lptr->defn.type != LBL_SPECIAL) {
+        /*
+         * WARN_LABEL_LATE defaults to an error, as this should never actually happen.
+         * Just in case this is a backwards compatibility problem, still make it a
+         * warning so that the user can suppress or demote it.
+         *
+         * As a special case, LBL_SPECIAL symbols are allowed to be changed
+         * even during the last pass.
+         */
+        nasm_error(ERR_WARNING|WARN_LABEL_LATE,
+                   "label `%s' %s during code generation",
+                   lptr->defn.label, created ? "defined" : "changed");
+    }
     lptr->defn.segment = segment;
     lptr->defn.offset  = offset;
     lptr->defn.size    = size;
diff --git a/include/error.h b/include/error.h
index cd64a497..3d2b7a1a 100644
--- a/include/error.h
+++ b/include/error.h
@@ -95,8 +95,7 @@ static inline vefunc nasm_set_verror(vefunc ve)
 #define WARN_MNP            	WARN( 1) /* macro-num-parameters warning */
 #define WARN_MSR            	WARN( 2) /* macro self-reference */
 #define WARN_MDP            	WARN( 3) /* macro default parameters check */
-#define WARN_OL             	WARN( 4) /* orphan label (no colon, and
-                                          * alone on line) */
+#define WARN_OL             	WARN( 4) /* orphan label (no colon, and alone on line) */
 #define WARN_NOV            	WARN( 5) /* numeric overflow */
 #define WARN_GNUELF         	WARN( 6) /* using GNU ELF extensions */
 #define WARN_FL_OVERFLOW    	WARN( 7) /* FP overflow */
@@ -115,9 +114,11 @@ static inline vefunc nasm_set_verror(vefunc ve)
 #define WARN_UNK_WARNING	WARN(20) /* unknown warning */
 #define WARN_NEG_REP		WARN(21) /* negative repeat count */
 #define WARN_PHASE		WARN(22) /* phase error in pass 1 */
+#define WARN_LABEL_REDEF	WARN(23) /* label redefined, but consistent */
+#define WARN_LABEL_LATE		WARN(24) /* label (re)defined during code generation */
 
 /* These two should come last */
-#define WARN_ALL		(22+2) /* Do not use WARN() here */
+#define WARN_ALL		(24+2) /* Do not use WARN() here */
 #define WARN_OTHER		WARN(WARN_ALL-1) /* any noncategorized warning */
 
 /* This is a bitmask */