From 3d92d615396d8b3f1c43ad59196e40f15a87bcc8 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Tue, 20 Feb 2024 03:10:25 +0100
Subject: Add the assume() macro

---
 src/ahoy/emulator.c   |  3 ---
 src/c8asm/assembler.c | 10 +++-------
 src/c8asm/parser.c    | 19 +++++++++----------
 src/common/macros.h   | 21 ++++++++-------------
 4 files changed, 20 insertions(+), 33 deletions(-)

(limited to 'src')

diff --git a/src/ahoy/emulator.c b/src/ahoy/emulator.c
index 8ecdc1b..c805fcd 100644
--- a/src/ahoy/emulator.c
+++ b/src/ahoy/emulator.c
@@ -314,9 +314,6 @@ opexec(uint16_t op)
 
 		break;
 	}
-
-	default:
-		unreachable();
 	}
 }
 
diff --git a/src/c8asm/assembler.c b/src/c8asm/assembler.c
index ffa9025..daafc11 100644
--- a/src/c8asm/assembler.c
+++ b/src/c8asm/assembler.c
@@ -77,23 +77,21 @@ assemble(FILE *stream, struct ast ast)
 	bool pad = false;
 
 	da_foreach (&ast, node) {
+		assume(node->kind == D_LABEL || node->kind == D_INSTR);
 		if (node->kind == D_LABEL) {
 			struct label lbl = {
 				.addr = i,
 				.sv = node->name,
 			};
 			pushlabel(node->name.p[0] == '.' ? &locals : &globals, lbl);
-		} else if (node->kind == D_INSTR)
+		} else
 			i += node->instr.kind == I_DB ? node->instr.len : 2;
-		else
-			unreachable();
 	}
 
 	da_foreach (&ast, node) {
 		if (node->kind == D_LABEL)
 			continue;
-		if (node->kind != D_INSTR)
-			unreachable();
+		assume(node->kind == D_INSTR);
 
 		/* Instructions need to be 0-padded so they appear on an even byte
 		   boundary. */
@@ -229,8 +227,6 @@ assemble(FILE *stream, struct ast ast)
 			PUT(0x8003 | (node->instr.args[0].val << 8)
 			    | node->instr.args[1].val << 4);
 			break;
-		default:
-			unreachable();
 		}
 	}
 
diff --git a/src/c8asm/parser.c b/src/c8asm/parser.c
index 208511d..01e13ae 100644
--- a/src/c8asm/parser.c
+++ b/src/c8asm/parser.c
@@ -119,14 +119,12 @@ parseop(void)
 struct raw_addr
 parseaddr(struct token tok)
 {
+	assume(tok.kind & (T_NUMBER | T_IDENT));
 	if (tok.kind == T_NUMBER)
 		return (struct raw_addr){.val = parsenum(tok, NS_ADDR)};
-	if (tok.kind == T_IDENT) {
-		if (regtype(tok.sv) != RT_NONE)
-			DIE_AT_POS_WITH_CODE(tok.sv, tok.sv.p, E_BADLABEL);
-		return (struct raw_addr){.label = true, .sv = tok.sv};
-	}
-	unreachable();
+	if (regtype(tok.sv) != RT_NONE)
+		DIE_AT_POS_WITH_CODE(tok.sv, tok.sv.p, E_BADLABEL);
+	return (struct raw_addr){.label = true, .sv = tok.sv};
 }
 
 enum regtype
@@ -150,6 +148,7 @@ regtype(struct u8view v)
 uint16_t
 hexval(char ch)
 {
+	assume((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f'));
 	return ch >= '0' && ch <= '9' ? ch - '0'
 	     : ch >= 'a' && ch <= 'f' ? ch - 'a' + 10
 	                              : (unreachable(), 0);
@@ -173,6 +172,9 @@ parsenum(struct token tok, enum numsize size)
 	}
 
 	for (ch = *v.p; v.len; v.p++, v.len--, ch = *v.p) {
+		assume((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f')
+		       || (ch >= 'A' && ch <= 'F') || ch == '\'');
+
 		if (ch == '\'')
 			continue;
 		else if (ch >= '0' && ch <= '9')
@@ -181,8 +183,6 @@ parsenum(struct token tok, enum numsize size)
 			ch -= 'a' - 10;
 		else if (ch >= 'A' && ch <= 'F')
 			ch -= 'A' - 10;
-		else
-			unreachable();
 
 		if (acc > cutoff || (acc == cutoff && ch > cutlim)) {
 			const char *s = size == NS_NIBBLE ? "nibble"
@@ -386,8 +386,7 @@ parseop_jp(void)
 			                     "v0-register or address", tokrepr(op.kind));
 		}
 		ins.args[ins.len++] = parseaddr(reqnext("address", T_NUMBER | T_IDENT));
-	} else
-		unreachable();
+	}
 
 	dapush(&ast, I(ins));
 }
diff --git a/src/common/macros.h b/src/common/macros.h
index 6daf08f..3735af6 100644
--- a/src/common/macros.h
+++ b/src/common/macros.h
@@ -9,19 +9,14 @@
 #define streq(x, y)    (!strcmp(x, y))
 #define u8eq(x, y)     (!u8cmp(x, y))
 
-#if DEBUG || !defined(unreachable)
-#	if DEBUG
-#		include "cerr.h"
-#		ifdef unreachable
-#			undef unreachable
-#		endif
-#		define unreachable() \
-			diex("%s:%d: hit unreachable in %s()", __FILE__, __LINE__, __func__)
-#	elifdef __clang__
-#		define unreachable() __builtin_unreachable()
-#	else
-#		include <stddef.h>
-#	endif
+#if DEBUG
+#	include "cerr.h"
+#	define assume(C) \
+		((C) ? (void)0 \
+		     : diex("%s:%d: %s(): assumption ‘%s’ failed", __FILE__, __LINE__, \
+		            __func__, #C))
+#else
+#	define assume(C) ((C) ? (void)0 : unreachable())
 #endif
 
 #endif /* !AHOY_COMMON_MACROS_H */
-- 
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