[gcc r17-3523] cobol: Allow larger REDEFINES for -dialect ibm.

https://gcc.gnu.org/g:4918feee536ef3ef5431f87f0b314f6b03378981

commit r17-3523-g4918feee536ef3ef5431f87f0b314f6b03378981
Author: James K. Lowden <[email protected]>
Date:   Thu Aug 20 17:58:09 2026 -0400

    cobol: Allow larger REDEFINES for -dialect ibm.
    
    ISO prohibits B REDEFINES A if B is larger than A, unless A is 01
    level and not external.  IBM and others do not impose the 01 restriction.
    
    Also simplify and correct how -preprocess parses its argument.
    
    gcc/cobol/ChangeLog:
    
            * cbldiag.h (enum cbl_diag_id_t): Define IsoRedefinesGrow.
            * cobol1.cc (cobol_langhook_handle_option): Handle Wredefines-grow.
            * lang-specs.h: Same.
            * lang.opt: Same.
            * lexio.cc (preprocess_filter_add): Use xstrdup, not std::vector.
            * messages.cc: Quell Wredefines-grow with -dialect ibm.
            * parse_ante.h (valid_redefine): Conditional message.

Diff:
---
 gcc/cobol/cbldiag.h    |  1 +
 gcc/cobol/cobol1.cc    |  4 ++++
 gcc/cobol/lang-specs.h |  1 +
 gcc/cobol/lang.opt     |  5 +++++
 gcc/cobol/lexio.cc     |  9 ++++-----
 gcc/cobol/messages.cc  |  6 ++++--
 gcc/cobol/parse_ante.h | 18 +++++++++---------
 7 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/gcc/cobol/cbldiag.h b/gcc/cobol/cbldiag.h
index 5f88e15563a6..c05bfde7f39f 100644
--- a/gcc/cobol/cbldiag.h
+++ b/gcc/cobol/cbldiag.h
@@ -189,6 +189,7 @@ enum cbl_diag_id_t : uint64_t {
   IbmVolatileW,  // dialect warning for ignored syntax
 
   IsoAssignFile,
+  IsoRedefinesGrow,
   IsoResume,
 
   MfAssignExternal,
diff --git a/gcc/cobol/cobol1.cc b/gcc/cobol/cobol1.cc
index eedaf600440a..79c6d507247e 100644
--- a/gcc/cobol/cobol1.cc
+++ b/gcc/cobol/cobol1.cc
@@ -645,6 +645,10 @@ cobol_langhook_handle_option (size_t scode,
           cobol_warning(MfRedefinesFirst, redefines_first, warning_as_error);
           return true;
 
+        case OPT_Wredefines_grow:
+          cobol_warning(IsoRedefinesGrow, redefines_grow, warning_as_error);
+          return true;
+
         case OPT_Wreturning_number:
           cobol_warning(MfReturningNum, returning_number, warning_as_error);
           return true;
diff --git a/gcc/cobol/lang-specs.h b/gcc/cobol/lang-specs.h
index 272ef480b6ae..701a1d1a07a8 100644
--- a/gcc/cobol/lang-specs.h
+++ b/gcc/cobol/lang-specs.h
@@ -91,6 +91,7 @@
 	"%{Wprocedure-pointer} %{Wno-procedure-pointer} "
 	"%{Wreplace-error} %{Wno-replace-error} "
 	"%{Wredefines-first} %{Wno-redefines-first} "
+	"%{Wredefines-grow} %{Wno-redefines-grow} "
 	"%{Wreturning-number} %{Wno-returning-number} "
 	"%{Wsegment-error} %{Wno-segment-error} "
 	"%{Wsegment-negative} %{Wno-segment-negative} "
diff --git a/gcc/cobol/lang.opt b/gcc/cobol/lang.opt
index 9e2f989b2626..8b0a575d1183 100644
--- a/gcc/cobol/lang.opt
+++ b/gcc/cobol/lang.opt
@@ -274,6 +274,11 @@ Wsegment
 Cobol Warning Var(cobol_segment, 1) Init(1)
 Warn if SECTION segments are used.
 
+; IsoRedefinesGrow, "-Wredefines-grow"
+Wredefines-grow
+Cobol Warning Var(redefines_grow, 1) Init(1)
+Warn if REDEFINES data item is larger than the redefined.
+
 ; IsoResume
 Wcobol-resume
 Cobol Warning Var(cobol_resume, 1) Init(1)
diff --git a/gcc/cobol/lexio.cc b/gcc/cobol/lexio.cc
index d4cb4a258f3c..f31f707ad02a 100644
--- a/gcc/cobol/lexio.cc
+++ b/gcc/cobol/lexio.cc
@@ -1443,12 +1443,11 @@ preprocess_filter_add( const char input[] ) {
   size_t pos = filter.find(",");
 
   if( pos != filter.npos ) {
-    std::vector<char> others( filter.size() - pos, '\0' );
-    std::copy( filter.begin() + pos + 1, filter.end(), others.begin() );
+    std::string args( filter.begin() + pos + 1, filter.end() );
     filter.resize(pos);
-    char *optstr = others.data();
-    for( char *opt = optstr + 1; (opt = strtok(opt, ",")); opt = NULL ) {
-      options.push_back(opt);
+
+    for( char *arg = xstrdup(args.c_str()); (arg = strtok(arg, ",")); arg = NULL ) {
+      options.push_back(arg);
     }
   }
 
diff --git a/gcc/cobol/messages.cc b/gcc/cobol/messages.cc
index e55ab194dd79..eff05f98e442 100644
--- a/gcc/cobol/messages.cc
+++ b/gcc/cobol/messages.cc
@@ -137,10 +137,12 @@ std::set<cbl_diag_t> cbl_diagnostics {
   { IbmVolatileE, "-Wcobol-volatile", diagnostics::kind::error, dialect_ibm_e },
   { IbmVolatileW, "-Wcobol-volatile", diagnostics::kind::warning, dialect_ibm_e },
 
-  // RESUME not supported by IBM
-  { IsoResume, "-Wcobol-resume", diagnostics::kind::error, dialect_ibm_e },
   // IBM, MF, and GNU all support ASSIGN TO filename, so we keep mum. 
   { IsoAssignFile, "-Wassign-file", diagnostics::kind::ignored, dialect_ibm_mf_gnu },
+  // ISO says for B REDEFINES A, Length(B) <= Length(A), others disagree
+  { IsoRedefinesGrow, "-Wredefines-grow", diagnostics::kind::error, dialect_ibm_mf_gnu },
+  // RESUME not supported by IBM
+  { IsoResume, "-Wcobol-resume", diagnostics::kind::error, dialect_ibm_e },
 
   { MfAnyLength, "-Wany-length", diagnostics::kind::error, dialect_mf_gnu },
   { MfAssignExternal, "-Wassign-external", diagnostics::kind::error, dialect_mf_gnu },
diff --git a/gcc/cobol/parse_ante.h b/gcc/cobol/parse_ante.h
index 243f43bbf1e7..2dff569a2b57 100644
--- a/gcc/cobol/parse_ante.h
+++ b/gcc/cobol/parse_ante.h
@@ -3145,8 +3145,6 @@ valid_redefine( const cbl_loc_t& loc,
             orig->level_str(), orig->name);
     return false;
   }
-  // We don't know about the redefining group until it's completely defined.
-
   /*
    * 8) The storage area required for the subject of the entry
    * shall not be larger than the storage area required for the
@@ -3159,13 +3157,15 @@ valid_redefine( const cbl_loc_t& loc,
       if( orig->level > 1 || orig->has_attr(external_e) ) {
         dbgmsg( "size error orig:  %s", field_str(orig) );
         dbgmsg( "size error redef: %s", field_str(field) );
-        error_msg(loc, "%s (%s size %u) larger than REDEFINES %s (%s size %u)",
-                  field->name,
-                  3 + cbl_field_type_str(field->type),
-                  field->size()/field->codeset.stride(),
-                  orig->name,
-                  3 + cbl_field_type_str(orig->type),
-                  orig->size()/field->codeset.stride() );
+        if( ! dialect_ok(loc, IsoRedefinesGrow, "REDEFINES larger") ) {
+          error_msg(loc, "%qs (%s size %u) larger than REDEFINES %qs (%s size %u)",
+                    field->name,
+                    3 + cbl_field_type_str(field->type),
+                    field->size()/field->codeset.stride(),
+                    orig->name,
+                    3 + cbl_field_type_str(orig->type),
+                    orig->size()/field->codeset.stride() );
+        }
       }
     }
   }