log_help: Include source_location

Use `std::experimental::source_location` because clang support is `??`
Add `ENABLE_SOURCE_LOCATION` make variable and corresponding `YOSYS_ENABLE_SOURCE_LOCATION` define.
Dummy out the struct if disabled and check for null instead of using `#ifdef` blocks everywhere.

Makefile

@@ -511,6 +511,9 @@ LIBS_VERIFIC += -Wl,--whole-archive $(patsubst %,$(VERIFIC_DIR)/%/*-linux.a,$(VE
 endif
 endif
 
+ifeq ($(ENABLE_SOURCE_LOCATION),1)
+CXXFLAGS += -DYOSYS_ENABLE_SOURCE_LOCATION
+endif
 
 ifeq ($(ENABLE_COVER),1)
 CXXFLAGS += -DYOSYS_ENABLE_COVER

kernel/log_help.cc

@@ -78,13 +78,15 @@ bool PrettyHelp::has_content()
 	return false;
 }
 
-void PrettyHelp::usage(const string &usage)
+void PrettyHelp::usage(const string &usage,
+	const source_location location)
 {
 	log_pass_str(usage, current_indent+1, true);
 	log("\n");
 }
 
-void PrettyHelp::option(const string &text, const string &description)
+void PrettyHelp::option(const string &text, const string &description,
+	const source_location location)
 {
 	open_option(text);
 	if (description.length()) {
@@ -94,23 +96,27 @@ void PrettyHelp::option(const string &text, const string &description)
 	close(1);
 }
 
-void PrettyHelp::codeblock(const string &code, const string &)
+void PrettyHelp::codeblock(const string &code, const string &,
+	const source_location location)
 {
 	log("%s\n", code.c_str());
 }
 
-void PrettyHelp::paragraph(const string &text)
+void PrettyHelp::paragraph(const string &text,
+	const source_location location)
 {
 	log_pass_str(text, current_indent);
 	log("\n");
 }
 
-void PrettyHelp::open_optiongroup(const string &)
+void PrettyHelp::open_optiongroup(const string &,
+	const source_location location)
 {
 	current_indent += 1;
 }
 
-void PrettyHelp::open_option(const string &text)
+void PrettyHelp::open_option(const string &text,
+	const source_location location)
 {
 	log_pass_str(text, current_indent);
 	current_indent += 1;

kernel/log_help.h

@@ -23,6 +23,19 @@
 #include "kernel/yosys_common.h"
 #include "kernel/json.h"
 
+#ifdef YOSYS_ENABLE_SOURCE_LOCATION
+#include <experimental/source_location>
+using std::experimental::source_location;
+#else
+struct source_location { // dummy placeholder
+	int line() const { return 0; }
+	int column() const { return 0; }
+	const char* file_name() const { return nullptr; }
+	const char* function_name() const { return nullptr; }
+	static const source_location current(...) { return source_location(); }
+};
+#endif
+
 YOSYS_NAMESPACE_BEGIN
 
 class PrettyHelp
@@ -37,13 +50,33 @@ public:
 
 	bool has_content();
 
-	void usage(const string &usage);
+	void usage(
-	void option(const string &text, const string &description = "");
+		const string &usage,
-	void codeblock(const string &code, const string &language = "none");
+		const source_location location = source_location::current()
-	void paragraph(const string &text);
+	);
+	void option(
+		const string &text,
+		const string &description = "",
+		const source_location location = source_location::current()
+	);
+	void codeblock(
+		const string &code,
+		const string &language = "none",
+		const source_location location = source_location::current()
+	);
+	void paragraph(
+		const string &text,
+		const source_location location = source_location::current()
+	);
 
-	void open_optiongroup(const string &group = "");
+	void open_optiongroup(
-	void open_option(const string &text);
+		const string &group = "",
+		const source_location location = source_location::current()
+	);
+	void open_option(
+		const string &text,
+		const source_location location = source_location::current()
+	);
 	void close(int levels = 1);
 };