fix handling of escaped chars in json backend and frontend

Makefile

@@ -915,7 +915,7 @@ clean:
 	rm -rf tests/simple/*.out tests/simple/*.log
 	rm -rf tests/memories/*.out tests/memories/*.log tests/memories/*.dmp
 	rm -rf tests/sat/*.log tests/techmap/*.log tests/various/*.log
-	rm -rf tests/bram/temp tests/fsm/temp tests/realmath/temp tests/share/temp tests/smv/temp
+	rm -rf tests/bram/temp tests/fsm/temp tests/realmath/temp tests/share/temp tests/smv/temp tests/various/temp
 	rm -rf vloghtb/Makefile vloghtb/refdat vloghtb/rtl vloghtb/scripts vloghtb/spec vloghtb/check_yosys vloghtb/vloghammer_tb.tar.bz2 vloghtb/temp vloghtb/log_test_*
 	rm -f tests/svinterfaces/*.log_stdout tests/svinterfaces/*.log_stderr tests/svinterfaces/dut_result.txt tests/svinterfaces/reference_result.txt tests/svinterfaces/a.out tests/svinterfaces/*_syn.v tests/svinterfaces/*.diff
 	rm -f  tests/tools/cmp_tbdata

backends/json/json.cc

@@ -52,8 +52,23 @@ struct JsonWriter
 		string newstr = "\"";
 		for (char c : str) {
 			if (c == '\\')
+				newstr += "\\\\";
+			else if (c == '"')
+				newstr += "\\\"";
+			else if (c == '\b')
+				newstr += "\\b";
+			else if (c == '\f')
+				newstr += "\\f";
+			else if (c == '\n')
+				newstr += "\\n";
+			else if (c == '\r')
+				newstr += "\\r";
+			else if (c == '\t')
+				newstr += "\\t";
+			else if (c < 0x20)
+				newstr += stringf("\\u%04X", c);
+			else
 				newstr += c;
-			newstr += c;
 		}
 		return newstr + "\"";
 	}

frontends/json/jsonparse.cc

@@ -60,10 +60,38 @@ struct JsonNode
 						break;
 
 					if (ch == '\\') {
-						int ch = f.get();
+						ch = f.get();
 
-						if (ch == EOF)
-							log_error("Unexpected EOF in JSON string.\n");
+						switch (ch) {
+							case EOF: log_error("Unexpected EOF in JSON string.\n"); break;
+							case '"':
+							case '/':
+							case '\\':           break;
+							case 'b': ch = '\b'; break;
+							case 'f': ch = '\f'; break;
+							case 'n': ch = '\n'; break;
+							case 'r': ch = '\r'; break;
+							case 't': ch = '\t'; break;
+							case 'u':
+								int val = 0;
+								for (int i = 0; i < 4; i++) {
+									ch = f.get();
+									val <<= 4;
+									if (ch >= '0' && '9' >= ch) {
+										val += ch - '0';
+									} else if (ch >= 'A' && 'F' >= ch) {
+										val += 10 + ch - 'A';
+									} else if (ch >= 'a' && 'f' >= ch) {
+										val += 10 + ch - 'a';
+									} else
+										log_error("Unexpected non-digit character in \\uXXXX sequence: %c.\n", ch);
+								}
+								if (val < 128)
+									ch = val;
+								else
+									log_error("Unsupported \\uXXXX sequence in JSON string: %04X.\n", val);
+								break;
+						}
 					}
 
 					data_string += ch;

tests/various/.gitignore

@@ -5,3 +5,4 @@
 /run-test.mk
 /plugin.so
 /plugin.so.dSYM
+/temp

tests/various/json_escape_chars.ys

@@ -0,0 +1,14 @@
+! mkdir -p temp
+read_verilog <<EOT
+(* src = "\042 \057 \134 \010 \014 \012 \015 \011 \025 \033" *)
+module foo;
+endmodule
+EOT
+write_json temp/test_escapes.json
+design -reset
+read_json temp/test_escapes.json
+write_json temp/test_escapes.json
+design -reset
+read_json temp/test_escapes.json
+write_rtlil temp/test_escapes.json.il
+! grep -F 'attribute \src "\" / \\ \010 \014 \n \015 \t \025 \033"' temp/test_escapes.json.il