From 5e1a570b75d5f5edf41be6c1409c283ca768e7e6 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Thu, 2 Sep 2021 12:03:25 -0700
Subject: pp: Implement #line directives and gcc line markers

Fixes #66.
---
 cc.h      |  1 +
 configure |  2 +-
 pp.c      | 23 ++++++++++++++++++++---
 scan.c    |  6 ++++++
 4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/cc.h b/cc.h
index a996541..3b33e8c 100644
--- a/cc.h
+++ b/cc.h
@@ -383,6 +383,7 @@ _Noreturn void error(const struct location *, const char *, ...);
 
 void scanfrom(const char *, FILE *);
 void scanopen(void);
+void scansetloc(struct location loc);
 void scan(struct token *);
 
 /* preprocessor */
diff --git a/configure b/configure
index 1d8a0f2..7b8555d 100755
--- a/configure
+++ b/configure
@@ -139,7 +139,7 @@ static const char target[]               = "$target";
 static const char *const startfiles[]    = {$startfiles};
 static const char *const endfiles[]      = {$endfiles};
 static const char *const preprocesscmd[] = {
-	"$DEFAULT_PREPROCESSOR", "-P",
+	"$DEFAULT_PREPROCESSOR", "-E",
 
 	/* clear preprocessor GNU C version */
 	"-U", "__GNUC__",
diff --git a/pp.c b/pp.c
index 9f0c74d..96f76fc 100644
--- a/pp.c
+++ b/pp.c
@@ -302,15 +302,18 @@ undef(void)
 static void
 directive(void)
 {
+	struct location newloc;
 	enum ppflags oldflags;
-	char *name;
+	char *name = NULL;
 
 	scan(&tok);
 	if (tok.kind == TNEWLINE)
 		return;  /* empty directive */
 	oldflags = ppflags;
 	ppflags |= PPNEWLINE;
-	name = tokencheck(&tok, TIDENT, "or newline after '#'");
+	if (tok.kind == TNUMBER)
+		goto line;  /* gcc line markers */
+	name = tokencheck(&tok, TIDENT, "newline, or number after '#'");
 	if (strcmp(name, "if") == 0) {
 		error(&tok.loc, "#if directive is not implemented");
 	} else if (strcmp(name, "ifdef") == 0) {
@@ -330,7 +333,21 @@ directive(void)
 		scan(&tok);
 		undef();
 	} else if (strcmp(name, "line") == 0) {
-		error(&tok.loc, "#line directive is not implemented");
+		scan(&tok);
+		tokencheck(&tok, TNUMBER, "after #line");
+line:
+		newloc.line = strtoull(tok.lit, NULL, 0);
+		scan(&tok);
+		newloc.file = tok.loc.file;
+		if (tok.kind == TSTRINGLIT) {
+			/* XXX: handle escape sequences (reuse string decoding from expr.c) */
+			newloc.file = strchr(tok.lit, '"') + 1;
+			*strchr(newloc.file, '"') = '\0';
+			scan(&tok);
+		}
+		while (tok.kind == TNUMBER)
+			scan(&tok);
+		scansetloc(newloc);
 	} else if (strcmp(name, "error") == 0) {
 		error(&tok.loc, "#error directive is not implemented");
 	} else if (strcmp(name, "pragma") == 0) {
diff --git a/scan.c b/scan.c
index 34e003e..a8327bf 100644
--- a/scan.c
+++ b/scan.c
@@ -444,6 +444,12 @@ scanopen(void)
 	}
 }
 
+void
+scansetloc(struct location loc)
+{
+	scanner->loc = loc;
+}
+
 static void
 scanclose(void)
 {
-- 
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