diff --git a/regression/ansi-c/linking_conflicts1/test.desc b/regression/ansi-c/linking_conflicts1/test.desc
index fb6ea7a29093..67ae329fc065 100644
--- a/regression/ansi-c/linking_conflicts1/test.desc
+++ b/regression/ansi-c/linking_conflicts1/test.desc
@@ -3,7 +3,7 @@ main.c
 other.c
 ^EXIT=(64|1)$
 ^SIGNAL=0$
-error: conflicting function declarations 'bar'
-error: conflicting function declarations 'bar2'
+conflicting function declarations 'bar'
+conflicting function declarations 'bar2'
 --
 ^warning: ignoring
diff --git a/regression/ansi-c/linking_conflicts2/test.desc b/regression/ansi-c/linking_conflicts2/test.desc
index f579050c99b9..80197d8fdfc4 100644
--- a/regression/ansi-c/linking_conflicts2/test.desc
+++ b/regression/ansi-c/linking_conflicts2/test.desc
@@ -3,6 +3,6 @@ main.c
 other.c
 ^EXIT=(64|1)$
 ^SIGNAL=0$
-error: conflicting function declarations 'foo'
+conflicting function declarations 'foo'
 --
 ^warning: ignoring
diff --git a/src/ansi-c/c_typecheck_base.cpp b/src/ansi-c/c_typecheck_base.cpp
index c9288a940c1a..bd5d805d0197 100644
--- a/src/ansi-c/c_typecheck_base.cpp
+++ b/src/ansi-c/c_typecheck_base.cpp
@@ -318,7 +318,7 @@ void c_typecheck_baset::typecheck_redefinition_non_type(
     if(final_old.id()!=ID_code)
     {
       error().source_location=new_symbol.location;
-      error() << "error: function symbol '" << new_symbol.display_name()
+      error() << "function symbol '" << new_symbol.display_name()
               << "' redefined with a different type:\n"
               << "Original: " << to_string(old_symbol.type) << "\n"
               << "     New: " << to_string(new_symbol.type) << eom;
@@ -613,9 +613,8 @@ void c_typecheck_baset::apply_asm_label(
       if(asm_label_map[orig_name]!=asm_label)
       {
         error().source_location=symbol.location;
-        error() << "error: replacing asm renaming "
-                << asm_label_map[orig_name] << " by "
-                << asm_label << eom;
+        error() << "replacing asm renaming " << asm_label_map[orig_name]
+                << " by " << asm_label << eom;
         throw 0;
       }
     }
diff --git a/src/ansi-c/c_typecheck_code.cpp b/src/ansi-c/c_typecheck_code.cpp
index 30e431fdef9e..a8634cc3a2fd 100644
--- a/src/ansi-c/c_typecheck_code.cpp
+++ b/src/ansi-c/c_typecheck_code.cpp
@@ -601,14 +601,6 @@ void c_typecheck_baset::typecheck_ifthenelse(code_ifthenelset &code)
 
   typecheck_expr(cond);
 
-  #if 0
-  if(cond.id()==ID_sideeffect &&
-     cond.get(ID_statement)==ID_assign)
-  {
-    warning("warning: assignment in if condition");
-  }
-  #endif
-
   implicit_typecast_bool(cond);
 
   if(code.then_case().get_statement() == ID_decl_block)
diff --git a/src/ansi-c/c_typecheck_expr.cpp b/src/ansi-c/c_typecheck_expr.cpp
index 022f5c4b4f93..c711dc21b1e5 100644
--- a/src/ansi-c/c_typecheck_expr.cpp
+++ b/src/ansi-c/c_typecheck_expr.cpp
@@ -1822,7 +1822,7 @@ void c_typecheck_baset::typecheck_expr_side_effect(side_effect_exprt &expr)
     if(type0.get_bool(ID_C_constant))
     {
       error().source_location = op0.source_location();
-      error() << "error: '" << to_string(op0) << "' is constant" << eom;
+      error() << "'" << to_string(op0) << "' is constant" << eom;
       throw 0;
     }
 
diff --git a/src/ansi-c/c_typecheck_typecast.cpp b/src/ansi-c/c_typecheck_typecast.cpp
index d0daeeec15ee..b66cd72f579b 100644
--- a/src/ansi-c/c_typecheck_typecast.cpp
+++ b/src/ansi-c/c_typecheck_typecast.cpp
@@ -34,7 +34,7 @@ void c_typecheck_baset::implicit_typecast(
   for(const auto &tc_warning : c_typecast.warnings)
   {
     warning().source_location=expr.find_source_location();
-    warning() << "warning: conversion from '" << to_string(src_type) << "' to '"
+    warning() << "conversion from '" << to_string(src_type) << "' to '"
               << to_string(dest_type) << "': " << tc_warning << eom;
   }
 }
diff --git a/src/cpp/cpp_declarator_converter.cpp b/src/cpp/cpp_declarator_converter.cpp
index 48f8629e34b1..afb1424cfb42 100644
--- a/src/cpp/cpp_declarator_converter.cpp
+++ b/src/cpp/cpp_declarator_converter.cpp
@@ -174,8 +174,7 @@ symbolt &cpp_declarator_convertert::convert(
       if(symbol_expr.id() != ID_type)
       {
         cpp_typecheck.error().source_location=name.source_location();
-        cpp_typecheck.error() << "error: expected type"
-                              << messaget::eom;
+        cpp_typecheck.error() << "expected type" << messaget::eom;
         throw 0;
       }
 
diff --git a/src/cpp/cpp_typecheck_bases.cpp b/src/cpp/cpp_typecheck_bases.cpp
index 5992ef58c680..e53f8ef1a78b 100644
--- a/src/cpp/cpp_typecheck_bases.cpp
+++ b/src/cpp/cpp_typecheck_bases.cpp
@@ -131,7 +131,7 @@ void cpp_typecheckt::add_base_components(
   if(bases.find(from_name)!=bases.end())
   {
     error().source_location=to.source_location();
-    error() << "error: non-virtual base class " << from_name
+    error() << "non-virtual base class " << from_name
             << " inherited multiple times" << eom;
     throw 0;
   }
diff --git a/src/cpp/cpp_typecheck_code.cpp b/src/cpp/cpp_typecheck_code.cpp
index 1e35036ceb9b..a5589576e6f3 100644
--- a/src/cpp/cpp_typecheck_code.cpp
+++ b/src/cpp/cpp_typecheck_code.cpp
@@ -275,10 +275,10 @@ void cpp_typecheckt::typecheck_member_initializer(codet &code)
       if(access == ID_private || access == ID_noaccess)
       {
         #if 0
-        error().source_location=code.source_location());
-        str << "error: constructor of '"
-            << to_string(symbol_expr)
-            << "' is not accessible";
+        error().source_location=code.find_source_location();
+        error() << "constructor of '"
+                << to_string(symbol_expr)
+                << "' is not accessible" << eom;
         throw 0;
         #endif
       }
diff --git a/src/cpp/cpp_typecheck_compound_type.cpp b/src/cpp/cpp_typecheck_compound_type.cpp
index a601f9e6f7fd..ca90ef35f2f6 100644
--- a/src/cpp/cpp_typecheck_compound_type.cpp
+++ b/src/cpp/cpp_typecheck_compound_type.cpp
@@ -205,8 +205,7 @@ void cpp_typecheckt::typecheck_compound_type(
       else
       {
         error().source_location=type.source_location();
-        error() << "error: compound tag '" << base_name
-                << "' declared previously\n"
+        error() << "compound tag '" << base_name << "' declared previously\n"
                 << "location of previous definition: " << symbol.location
                 << eom;
         throw 0;
@@ -1518,9 +1517,8 @@ bool cpp_typecheckt::get_component(
         else
         {
           error().source_location=source_location;
-          error() << "error: member '" << component_name
-                  << "' is not accessible (" << component.get(ID_access) << ")"
-                  << eom;
+          error() << "member '" << component_name << "' is not accessible ("
+                  << component.get(ID_access) << ")" << eom;
           throw 0;
         }
       }
@@ -1554,8 +1552,8 @@ bool cpp_typecheckt::get_component(
           if(check_component_access(component, final_type))
           {
             error().source_location=source_location;
-            error() << "error: member '" << component_name
-                    << "' is not accessible" << eom;
+            error() << "member '" << component_name << "' is not accessible"
+                    << eom;
             throw 0;
           }
 
diff --git a/src/cpp/cpp_typecheck_enum_type.cpp b/src/cpp/cpp_typecheck_enum_type.cpp
index 2baa954307aa..2133b204390e 100644
--- a/src/cpp/cpp_typecheck_enum_type.cpp
+++ b/src/cpp/cpp_typecheck_enum_type.cpp
@@ -135,8 +135,7 @@ void cpp_typecheckt::typecheck_enum_type(typet &type)
     if(has_body)
     {
       error().source_location=type.source_location();
-      error() << "error: enum symbol '" << base_name
-              << "' declared previously\n"
+      error() << "enum symbol '" << base_name << "' declared previously\n"
               << "location of previous definition: " << symbol.location << eom;
       throw 0;
     }
diff --git a/src/cpp/cpp_typecheck_expr.cpp b/src/cpp/cpp_typecheck_expr.cpp
index 6048d129bdef..b42727b5de50 100644
--- a/src/cpp/cpp_typecheck_expr.cpp
+++ b/src/cpp/cpp_typecheck_expr.cpp
@@ -143,7 +143,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
       if(!standard_conversion_lvalue_to_rvalue(e1, expr.op1()))
       {
         error().source_location=e1.find_source_location();
-        error() << "error: lvalue to rvalue conversion" << eom;
+        error() << "lvalue to rvalue conversion" << eom;
         throw 0;
       }
     }
@@ -154,7 +154,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
       if(!standard_conversion_array_to_pointer(e1, expr.op1()))
       {
         error().source_location=e1.find_source_location();
-        error() << "error: array to pointer conversion" << eom;
+        error() << "array to pointer conversion" << eom;
         throw 0;
       }
     }
@@ -165,7 +165,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
       if(!standard_conversion_function_to_pointer(e1, expr.op1()))
       {
         error().source_location=e1.find_source_location();
-        error() << "error: function to pointer conversion" << eom;
+        error() << "function to pointer conversion" << eom;
         throw 0;
       }
     }
@@ -176,7 +176,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
       if(!standard_conversion_lvalue_to_rvalue(e2, expr.op2()))
       {
         error().source_location=e2.find_source_location();
-        error() << "error: lvalue to rvalue conversion" << eom;
+        error() << "lvalue to rvalue conversion" << eom;
         throw 0;
       }
     }
@@ -187,7 +187,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
       if(!standard_conversion_array_to_pointer(e2, expr.op2()))
       {
         error().source_location=e2.find_source_location();
-        error() << "error: array to pointer conversion" << eom;
+        error() << "array to pointer conversion" << eom;
         throw 0;
       }
     }
@@ -198,7 +198,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
       if(!standard_conversion_function_to_pointer(e2, expr.op2()))
       {
         error().source_location=expr.find_source_location();
-        error() << "error: function to pointer conversion" << eom;
+        error() << "function to pointer conversion" << eom;
         throw 0;
       }
     }
@@ -215,7 +215,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
     else
     {
       error().source_location=expr.find_source_location();
-      error() << "error: bad types for operands" << eom;
+      error() << "bad types for operands" << eom;
       throw 0;
     }
     return;
@@ -268,7 +268,7 @@ void cpp_typecheckt::typecheck_expr_trinary(if_exprt &expr)
     else
     {
       error().source_location=expr.find_source_location();
-      error() << "error: types are incompatible.\n"
+      error() << "types are incompatible.\n"
               << "I got '" << type2cpp(expr.op1().type(), *this) << "' and '"
               << type2cpp(expr.op2().type(), *this) << "'." << eom;
       throw 0;
@@ -701,7 +701,7 @@ void cpp_typecheckt::typecheck_expr_address_of(exprt &expr)
       if(code_type.get_bool(ID_C_is_virtual))
       {
         error().source_location=expr.source_location();
-        error() << "error: pointers to virtual methods"
+        error() << "pointers to virtual methods"
                 << " are currently not implemented" << eom;
         throw 0;
       }
@@ -1062,7 +1062,7 @@ void cpp_typecheckt::typecheck_expr_member(
   if(expr.operands().size()!=1)
   {
     error().source_location=expr.find_source_location();
-    error() << "error: member operator expects one operand" << eom;
+    error() << "member operator expects one operand" << eom;
     throw 0;
   }
 
@@ -1094,7 +1094,7 @@ void cpp_typecheckt::typecheck_expr_member(
      followed_op0_type.id()!=ID_union)
   {
     error().source_location=expr.find_source_location();
-    error() << "error: member operator requires struct/union type "
+    error() << "member operator requires struct/union type "
             << "on left hand side but got '" << to_string(followed_op0_type)
             << "'" << eom;
     throw 0;
@@ -1106,7 +1106,7 @@ void cpp_typecheckt::typecheck_expr_member(
   if(type.is_incomplete())
   {
     error().source_location = expr.find_source_location();
-    error() << "error: member operator got incomplete type "
+    error() << "member operator got incomplete type "
             << "on left hand side" << eom;
     throw 0;
   }
@@ -1153,7 +1153,7 @@ void cpp_typecheckt::typecheck_expr_member(
         to_code_type(symbol_expr.type()).return_type().id() == ID_constructor)
       {
         error().source_location=expr.find_source_location();
-        error() << "error: member '"
+        error() << "member '"
                 << lookup(symbol_expr.get(ID_identifier)).base_name
                 << "' is a constructor" << eom;
         throw 0;
@@ -1167,7 +1167,7 @@ void cpp_typecheckt::typecheck_expr_member(
         if(pcomp.is_nil())
         {
           error().source_location=expr.find_source_location();
-          error() << "error: '" << symbol_expr.get(ID_identifier)
+          error() << "'" << symbol_expr.get(ID_identifier)
                   << "' is not static member "
                   << "of class '" << to_string(op0.type()) << "'" << eom;
           throw 0;
@@ -1209,8 +1209,8 @@ void cpp_typecheckt::typecheck_expr_member(
   else
   {
     error().source_location=expr.find_source_location();
-    error() << "error: member '" << component_name << "' of '"
-            << to_string(type) << "' not found" << eom;
+    error() << "member '" << component_name << "' of '" << to_string(type)
+            << "' not found" << eom;
     throw 0;
   }
 
@@ -1239,7 +1239,7 @@ void cpp_typecheckt::typecheck_expr_ptrmember(
   if(expr.operands().size()!=1)
   {
     error().source_location=expr.find_source_location();
-    error() << "error: ptrmember operator expects one operand" << eom;
+    error() << "ptrmember operator expects one operand" << eom;
     throw 0;
   }
 
@@ -1250,7 +1250,7 @@ void cpp_typecheckt::typecheck_expr_ptrmember(
   if(op.type().id() != ID_pointer)
   {
     error().source_location=expr.find_source_location();
-    error() << "error: ptrmember operator requires pointer type "
+    error() << "ptrmember operator requires pointer type "
             << "on left hand side, but got '" << to_string(op.type()) << "'"
             << eom;
     throw 0;
diff --git a/src/cpp/cpp_typecheck_resolve.cpp b/src/cpp/cpp_typecheck_resolve.cpp
index 35d742e355ca..deacf8e70696 100644
--- a/src/cpp/cpp_typecheck_resolve.cpp
+++ b/src/cpp/cpp_typecheck_resolve.cpp
@@ -1649,9 +1649,8 @@ exprt cpp_typecheck_resolvet::resolve(
       return nil_exprt();
 
     cpp_typecheck.error().source_location=result.source_location());
-    cpp_typecheck.str
-      << "error: member '" << result.get(ID_component_name)
-      << "' is not accessible";
+    cpp_typecheck.error() << "member '" << result.get(ID_component_name)
+                          << "' is not accessible" << messaget::eom;
     throw 0;
     #endif
   }
@@ -1667,7 +1666,7 @@ exprt cpp_typecheck_resolvet::resolve(
       cpp_typecheck.error().source_location=source_location;
 
       cpp_typecheck.error()
-        << "error: expected expression, but got type '"
+        << "expected expression, but got type '"
         << cpp_typecheck.to_string(result.type()) << "'" << messaget::eom;
 
       throw 0;
@@ -1683,7 +1682,7 @@ exprt cpp_typecheck_resolvet::resolve(
       cpp_typecheck.error().source_location=source_location;
 
       cpp_typecheck.error()
-        << "error: expected type, but got expression '"
+        << "expected type, but got expression '"
         << cpp_typecheck.to_string(result) << "'" << messaget::eom;
 
       throw 0;
diff --git a/src/cpp/cpp_typecheck_type.cpp b/src/cpp/cpp_typecheck_type.cpp
index 9c034a432f1b..9ad47f3fa783 100644
--- a/src/cpp/cpp_typecheck_type.cpp
+++ b/src/cpp/cpp_typecheck_type.cpp
@@ -59,7 +59,7 @@ void cpp_typecheckt::typecheck_type(typet &type)
     if(symbol_expr.id()!=ID_type)
     {
       error().source_location=type.source_location();
-      error() << "error: expected type" << eom;
+      error() << "expected type" << eom;
       throw 0;
     }
 
diff --git a/src/goto-programs/builtin_functions.cpp b/src/goto-programs/builtin_functions.cpp
index 40e9bb0e1c9e..45db21457ef0 100644
--- a/src/goto-programs/builtin_functions.cpp
+++ b/src/goto-programs/builtin_functions.cpp
@@ -627,15 +627,15 @@ void goto_convertt::do_function_call_symbol(
   if(ns.lookup(identifier, symbol))
   {
     error().source_location=function.find_source_location();
-    error() << "error: function '" << identifier << "' not found" << eom;
+    error() << "function '" << identifier << "' not found" << eom;
     throw 0;
   }
 
   if(symbol->type.id()!=ID_code)
   {
     error().source_location=function.find_source_location();
-    error() << "error: function '" << identifier
-            << "' type mismatch: expected code" << eom;
+    error() << "function '" << identifier << "' type mismatch: expected code"
+            << eom;
     throw 0;
   }
 
diff --git a/src/linking/linking.cpp b/src/linking/linking.cpp
index 9dea1f00b9f6..473c0eeac58f 100644
--- a/src/linking/linking.cpp
+++ b/src/linking/linking.cpp
@@ -385,8 +385,7 @@ void linkingt::link_error(
 {
   error().source_location=new_symbol.location;
 
-  error() << "error: " << msg << " '" << old_symbol.display_name() << "'"
-          << '\n';
+  error() << msg << " '" << old_symbol.display_name() << "'" << '\n';
   error() << "old definition in module '" << old_symbol.module << "' "
           << old_symbol.location << '\n'
           << type_to_string_verbose(old_symbol) << '\n';
@@ -402,8 +401,8 @@ void linkingt::link_warning(
 {
   warning().source_location=new_symbol.location;
 
-  warning() << "warning: " << msg << " " << quote_begin
-            << old_symbol.display_name() << quote_end << '\n';
+  warning() << msg << " " << quote_begin << old_symbol.display_name()
+            << quote_end << '\n';
   warning() << "old definition in module " << old_symbol.module << " "
             << old_symbol.location << '\n'
             << type_to_string_verbose(old_symbol) << '\n';
@@ -1058,7 +1057,7 @@ void linkingt::duplicate_object_symbol(
       {
         warning().source_location=new_symbol.location;
 
-        warning() << "warning: conflicting initializers for"
+        warning() << "conflicting initializers for"
                   << " variable " << quote_begin << old_symbol.name << quote_end
                   << '\n';
         warning() << "using old value in module " << old_symbol.module << " "