Add warning class -Wno-declaration-after-use

With `-ggno-strict-parameter-declaration` a warning is issued for
parameter use before declaration.  This warning suppressed with
the new class `-Wno-declaration-after-use`, instead of `-Wno-anachronisms`.

Documentation/usage/command_line_flags.rst

@@ -136,7 +136,7 @@ These flags affect the general behavior of the compiler.
     The standards requires that parameters must be declared lexically
     before they are used.  Using -gno-strict-parameter-declaration
     will allow using a parameter before declaration, with a
-    warning. The warning can be suppressed with -Wno-anachronisms.
+    warning. The warning can be suppressed with -Wno-declaration-after-use.
 
   * shared-loop-index/no-shared-loop-index
 
@@ -267,6 +267,7 @@ These flags affect the general behavior of the compiler.
       -Wanachronisms
       -Wimplicit
       -Wimplicit-dimensions
+      -Wdeclaration-after-use
       -Wmacro-replacement
       -Wportbind
       -Wselect-range
@@ -295,6 +296,11 @@ These flags affect the general behavior of the compiler.
     This flag is supported in release 10.1 or master branch snapshots after
     2016-02-06.
 
+  * declaration-after-use
+
+    With -gno-strict-parameter-declaration, issue a warning when a
+    parameter is declared after it is used.
+
   * macro-redefinition
 
     This enables warnings when a macro is redefined, even if the macro text

compiler.h

@@ -104,6 +104,9 @@ extern bool warn_sens_entire_arr;
 /* Warn about level-appropriate anachronisms. */
 extern bool warn_anachronisms;
 
+/* Warn about declaration after use (unless flaged as errors). */
+extern bool warn_decl_after_use;
+
 /* Warn about nets that are references but not driven. */
 extern bool warn_floating_nets;
 

driver/iverilog.man.in

@@ -154,7 +154,7 @@ numbers are not truncated to integer width.
 The standards requires that parameters must be declared lexically
 before they are used.  Using \fB\-gno\-strict\-parameter\-declaration\fP
 will allow using a parameter before declaration, with a warning.
-The warning can be suppressed with -Wno-anachronisms.
+The warning can be suppressed with -Wno-declaration-after-use.
 .TP 8
 .B -gshared-loop-index\fI|\fP-gno-shared-loop-index
 Enable (default) or disable the exclusion of for-loop control variables
@@ -373,6 +373,11 @@ This enables warnings for creation of implicit declarations. For
 example, if a scalar wire X is used but not declared in the Verilog
 source, this will print a warning at its first use.
 
+.TP 8
+.B declaration-after-use
+This enables warnings for declarations after use, when
+those are not flagged as errors (default).  
+
 .TP 8
 .B macro-redefinition\fI | \fPmacro-replacement
 This enables preprocessor warnings when a macro is being redefined.

driver/main.c

@@ -143,7 +143,7 @@ int gen_std_include = 1;
    of the include list. */
 int gen_relative_include = 0;
 
-char warning_flags[17] = "n";
+char warning_flags[18] = "nu";
 
 int separate_compilation_flag = 0;
 
@@ -528,6 +528,7 @@ static void process_warning_switch(const char*name)
 {
       if (strcmp(name,"all") == 0) {
 	    process_warning_switch("anachronisms");
+	    process_warning_switch("declaration-after-use");
 	    process_warning_switch("implicit");
 	    process_warning_switch("implicit-dimensions");
 	    process_warning_switch("macro-replacement");
@@ -538,6 +539,9 @@ static void process_warning_switch(const char*name)
       } else if (strcmp(name,"anachronisms") == 0) {
 	    if (! strchr(warning_flags, 'n'))
 		  strcat(warning_flags, "n");
+      } else if (strcmp(name,"declaration-after-use") == 0) {
+	    if (! strchr(warning_flags, 'u'))
+		  strcat(warning_flags, "u");
       } else if (strcmp(name,"floating-nets") == 0) {
 	    if (! strchr(warning_flags, 'f'))
 		  strcat(warning_flags, "f");
@@ -579,6 +583,12 @@ static void process_warning_switch(const char*name)
 		  cp[0] = cp[1];
 		  cp += 1;
 	    }
+      } else if (strcmp(name,"no-declaration-after-use") == 0) {
+	    char*cp = strchr(warning_flags, 'u');
+	    if (cp) while (*cp) {
+		  cp[0] = cp[1];
+		  cp += 1;
+	    }
       } else if (strcmp(name,"no-floating-nets") == 0) {
 	    char*cp = strchr(warning_flags, 'f');
 	    if (cp) while (*cp) {

main.cc

@@ -173,6 +173,7 @@ bool warn_ob_select = false;
 bool warn_sens_entire_vec = false;
 bool warn_sens_entire_arr = false;
 bool warn_anachronisms = false;
+bool warn_decl_after_use = false;
 bool warn_floating_nets = false;
 
 /*
@@ -767,6 +768,9 @@ static void read_iconfig_file(const char*ipath)
 		      case 'n':
 			warn_anachronisms = true;
 			break;
+		      case 'u':
+			warn_decl_after_use = true;
+			break;
 		      default:
 			break;
 		  }

symbol_search.cc

@@ -196,7 +196,7 @@ bool symbol_search(const LineInfo*li, Design*des, NetScope*scope,
 			      res->scope = scope;
 			      res->par_val = par;
 			      res->path_head = path;
-			      if (warn_anachronisms && decl_after_use) {
+			      if (warn_decl_after_use && decl_after_use) {
 				      cerr << li->get_fileline()
 					   << ": warning: parameter `" << path_tail.name
 					   << "` used before declaration." << endl;