Don't report "Warning 202: Error: ..."

An invalid preprocessor expression is reported as a pair of
warnings with the second giving a more detailed message from the
expression evaluator.  Previously SWIG prefixed the second message
with "Error:" - that was confusing as it's actually only a warning
by default so we've now dropped this prefix.

Before:

x.i:1: Warning 202: Could not evaluate expression '1.2'
x.i:1: Warning 202: Error: 'Floating point constant in preprocessor expression'

Now:

x.i:1: Warning 202: Could not evaluate expression '1.2'
x.i:1: Warning 202: Floating point constant in preprocessor expression

See swig#1465

Author: ojwb

CHANGES.current

@@ -7,6 +7,23 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2022-02-24: olly
+	    #1465 An invalid preprocessor expression is reported as a pair of
+	    warnings with the second giving a more detailed message from the
+	    expression evaluator.  Previously SWIG prefixed the second message
+	    with "Error:" - that was confusing as it's actually only a warning
+	    by default so we've now dropped this prefix.
+
+	    Before:
+
+	    x.i:1: Warning 202: Could not evaluate expression '1.2'
+	    x.i:1: Warning 202: Error: 'Floating point constant in preprocessor expression'
+
+	    Now:
+
+	    x.i:1: Warning 202: Could not evaluate expression '1.2'
+	    x.i:1: Warning 202: Floating point constant in preprocessor expression
+
 2022-02-23: olly
 	    #1384 Fix a preprocessor expression evaluation bug.  A
 	    subexpression in parentheses lost its string/int type flag and

Examples/test-suite/errors/pp_badeval.stderr

@@ -1,2 +1,2 @@
 pp_badeval.i:4: Warning 202: Could not evaluate expression 'FOO==4+'
-pp_badeval.i:4: Warning 202: Error: 'Expected an expression'
+pp_badeval.i:4: Warning 202: Expected an expression

Examples/test-suite/errors/pp_expressions_bad.stderr

@@ -1,23 +1,23 @@
 pp_expressions_bad.i:7: Warning 202: Could not evaluate expression '1%ZERO'
-pp_expressions_bad.i:7: Warning 202: Error: 'Modulo by zero in expression'
+pp_expressions_bad.i:7: Warning 202: Modulo by zero in expression
 pp_expressions_bad.i:9: Warning 202: Could not evaluate expression '2/ZERO'
-pp_expressions_bad.i:9: Warning 202: Error: 'Division by zero in expression'
+pp_expressions_bad.i:9: Warning 202: Division by zero in expression
 pp_expressions_bad.i:12: Warning 202: Could not evaluate expression '1%(5-5)'
-pp_expressions_bad.i:12: Warning 202: Error: 'Modulo by zero in expression'
+pp_expressions_bad.i:12: Warning 202: Modulo by zero in expression
 pp_expressions_bad.i:14: Warning 202: Could not evaluate expression '2/(55-55)'
-pp_expressions_bad.i:14: Warning 202: Error: 'Division by zero in expression'
+pp_expressions_bad.i:14: Warning 202: Division by zero in expression
 pp_expressions_bad.i:18: Warning 202: Could not evaluate expression '1.2'
-pp_expressions_bad.i:18: Warning 202: Error: 'Floating point constant in preprocessor expression'
+pp_expressions_bad.i:18: Warning 202: Floating point constant in preprocessor expression
 pp_expressions_bad.i:21: Warning 202: Could not evaluate expression '2e3'
-pp_expressions_bad.i:21: Warning 202: Error: 'Floating point constant in preprocessor expression'
+pp_expressions_bad.i:21: Warning 202: Floating point constant in preprocessor expression
 pp_expressions_bad.i:25: Warning 202: Could not evaluate expression '8.8'
-pp_expressions_bad.i:25: Warning 202: Error: 'Floating point constant in preprocessor expression'
+pp_expressions_bad.i:25: Warning 202: Floating point constant in preprocessor expression
 pp_expressions_bad.i:29: Error: Unknown SWIG preprocessor directive: if123 (if this is a block of target language code, delimit it with %{ and %})
 pp_expressions_bad.i:30: Error: Extraneous #endif.
 pp_expressions_bad.i:32: Error: Unknown SWIG preprocessor directive: if456e (if this is a block of target language code, delimit it with %{ and %})
 pp_expressions_bad.i:33: Error: Extraneous #endif.
 pp_expressions_bad.i:42: Warning 204: CPP #warning, "Warning okay: #if(1)".
 pp_expressions_bad.i:48: Warning 202: Could not evaluate expression '"TWO" == 1'
-pp_expressions_bad.i:48: Warning 202: Error: 'Can't mix strings and integers in expression'
+pp_expressions_bad.i:48: Warning 202: Can't mix strings and integers in expression
 pp_expressions_bad.i:52: Warning 202: Could not evaluate expression '1 == ("TWO")'
-pp_expressions_bad.i:52: Warning 202: Error: 'Can't mix strings and integers in expression'
+pp_expressions_bad.i:52: Warning 202: Can't mix strings and integers in expression

Examples/test-suite/errors/pp_invalid_exponents.stderr

@@ -1,6 +1,6 @@
 :EOF: Error: Exponent does not have any digits
 pp_invalid_exponents.i:3: Warning 202: Could not evaluate expression '123e'
-pp_invalid_exponents.i:3: Warning 202: Error: 'Syntax error'
+pp_invalid_exponents.i:3: Warning 202: Syntax error
 :EOF: Error: Exponent does not have any digits
 pp_invalid_exponents.i:6: Warning 202: Could not evaluate expression '456.e'
-pp_invalid_exponents.i:6: Warning 202: Error: 'Syntax error'
+pp_invalid_exponents.i:6: Warning 202: Syntax error

Source/Preprocessor/cpp.c

@@ -1686,7 +1686,7 @@ String *Preprocessor_parse(String *s) {
 	      Seek(value, 0, SEEK_SET);
 	      Swig_warning(WARN_PP_EVALUATION, Getfile(value), Getline(value), "Could not evaluate expression '%s'\n", value);
 	      if (msg)
-		Swig_warning(WARN_PP_EVALUATION, Getfile(value), Getline(value), "Error: '%s'\n", msg);
+		Swig_warning(WARN_PP_EVALUATION, Getfile(value), Getline(value), "%s\n", msg);
 	      allow = 0;
 	    } else {
 	      if (val == 0)
@@ -1720,7 +1720,7 @@ String *Preprocessor_parse(String *s) {
 		Seek(value, 0, SEEK_SET);
 		Swig_warning(WARN_PP_EVALUATION, Getfile(value), Getline(value), "Could not evaluate expression '%s'\n", value);
 		if (msg)
-		  Swig_warning(WARN_PP_EVALUATION, Getfile(value), Getline(value), "Error: '%s'\n", msg);
+		  Swig_warning(WARN_PP_EVALUATION, Getfile(value), Getline(value), "%s\n", msg);
 		allow = 0;
 	      } else {
 		if (val)