From b428bf4600774b49de780e1dae7ff00f6564e72f Mon Sep 17 00:00:00 2001
From: Emily Schmidt <emily@yosyshq.com>
Date: Tue, 27 Aug 2024 13:10:34 +0100
Subject: [PATCH] functional backends: identifiers in c++/smtlib may not start
 with digits

---
 backends/functional/cxx.cc    | 4 ++--
 backends/functional/smtlib.cc | 4 ++--
 kernel/functional.h           | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/backends/functional/cxx.cc b/backends/functional/cxx.cc
index 282eb8f67..de7737a42 100644
--- a/backends/functional/cxx.cc
+++ b/backends/functional/cxx.cc
@@ -48,8 +48,8 @@ template<typename Id> struct CxxScope : public Functional::Scope<Id> {
 		for(const char **p = reserved_keywords; *p != nullptr; p++)
 			this->reserve(*p);
 	}
-	bool is_character_legal(char c) override {
-		return isascii(c) && (isalnum(c) || c == '_' || c == '$');
+	bool is_character_legal(char c, int index) override {
+		return isascii(c) && (isalpha(c) || (isdigit(c) && index > 0) || c == '_' || c == '$');
 	}
 };
 
diff --git a/backends/functional/smtlib.cc b/backends/functional/smtlib.cc
index 4e176c2fd..ae6ae40ca 100644
--- a/backends/functional/smtlib.cc
+++ b/backends/functional/smtlib.cc
@@ -48,8 +48,8 @@ struct SmtScope : public Functional::Scope<int> {
 		for(const char **p = reserved_keywords; *p != nullptr; p++)
 			reserve(*p);
 	}
-	bool is_character_legal(char c) override {
-		return isascii(c) && (isalnum(c) || strchr("~!@$%^&*_-+=<>.?/", c));
+	bool is_character_legal(char c, int index) override {
+		return isascii(c) && (isalpha(c) || (isdigit(c) && index > 0) || strchr("~!@$%^&*_-+=<>.?/", c));
 	}
 };
 
diff --git a/kernel/functional.h b/kernel/functional.h
index bc7b86ac1..2afdd7fc3 100644
--- a/kernel/functional.h
+++ b/kernel/functional.h
@@ -576,7 +576,7 @@ namespace Functional {
 	template<class Id> class Scope {
 	protected:
 		char substitution_character = '_';
-		virtual bool is_character_legal(char) = 0;
+		virtual bool is_character_legal(char, int) = 0;
 	private:
 		pool<std::string> _used_names;
 		dict<Id, std::string> _by_id;
@@ -587,7 +587,7 @@ namespace Functional {
 		std::string unique_name(IdString suggestion) {
 			std::string str = RTLIL::unescape_id(suggestion);
 			for(size_t i = 0; i < str.size(); i++)
-				if(!is_character_legal(str[i]))
+				if(!is_character_legal(str[i], i))
 					str[i] = substitution_character;
 			if(_used_names.count(str) == 0) {
 				_used_names.insert(str);