From 068d5b3d203f6c3e1536cef6397d31133d143a57 Mon Sep 17 00:00:00 2001
From: Michael Matz <matz@suse.de>
Date: Wed, 3 Jun 2020 18:38:11 +0200
Subject: [PATCH] pp: Move errors about stray backslashes

they were emitted too early, in particular also in macro
substitution which might turn out to not be stray in case it's
further stringified.  Check in next() instead.  Add two testcases
that an error is still emitted for obvious top-level baskslashes,
and that stringifying such a thing works.
---
 tccpp.c                                    | 5 ++---
 tests/tcctest.c                            | 3 +++
 tests/tests2/60_errors_and_warnings.c      | 3 +++
 tests/tests2/60_errors_and_warnings.expect | 3 +++
 4 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/tccpp.c b/tccpp.c
index c4c1ce53..1c2c8bc9 100644
--- a/tccpp.c
+++ b/tccpp.c
@@ -3511,8 +3511,6 @@ static void macro_subst(
             if (tok_str->len)
                 spc = is_space(t = tok_str->str[tok_str->lastlen]);
         } else {
-            if (t == '\\' && !(parse_flags & PARSE_FLAG_ACCEPT_STRAYS))
-                tcc_error("stray '\\' in program");
 no_subst:
             if (!check_space(t, &spc))
                 tok_str_add2(tok_str, t, &cval);
@@ -3569,7 +3567,8 @@ ST_FUNC void next(void)
     } else if (tok == TOK_PPSTR) {
         if (parse_flags & PARSE_FLAG_TOK_STR)
             parse_string((char *)tokc.str.data, tokc.str.size - 1);
-    }
+    } else if (tok == '\\' && !(parse_flags & PARSE_FLAG_ACCEPT_STRAYS))
+        tcc_error("stray '\\' in program");
 }
 
 /* push back current token and set current token to 'last_tok'. Only
diff --git a/tests/tcctest.c b/tests/tcctest.c
index 1c12dc31..a866330e 100644
--- a/tests/tcctest.c
+++ b/tests/tcctest.c
@@ -420,6 +420,9 @@ comment
     have_included_42test_h = 1;
     have_included_42test_h_second = 1;
     have_included_42test_h_third = 1;
+
+    /* Check that we don't complain about stray \ here */
+    printf("print a backslash: %s\n", stringify(\\));
 }
 
 
diff --git a/tests/tests2/60_errors_and_warnings.c b/tests/tests2/60_errors_and_warnings.c
index ac331ebb..19b7f0c1 100644
--- a/tests/tests2/60_errors_and_warnings.c
+++ b/tests/tests2/60_errors_and_warnings.c
@@ -318,5 +318,8 @@ int main()
     int n = _Generic(*a, double:0, long double:1);
 }
 
+#elif defined test_stray_backslash
+#define x \a
+x
 /******************************************************************/
 #endif
diff --git a/tests/tests2/60_errors_and_warnings.expect b/tests/tests2/60_errors_and_warnings.expect
index 838f6fcc..d693f91a 100644
--- a/tests/tests2/60_errors_and_warnings.expect
+++ b/tests/tests2/60_errors_and_warnings.expect
@@ -150,3 +150,6 @@ bar  : 3 ; 3
 
 [test_long_double_type_for_win32]
 60_errors_and_warnings.c:317: warning: assignment from incompatible pointer type
+
+[test_stray_backslash]
+60_errors_and_warnings.c:323: error: stray '\' in program