[gcc r12-2890] libcpp: Fix ICE with -Wtraditional preprocessing [PR101638]

[gcc r12-2890] libcpp: Fix ICE with -Wtraditional preprocessing [PR101638]

[Jakub Jelinek]

https://gcc.gnu.org/g:408d88af60e3268f7fad59fa393ec7e28922c435

commit r12-2890-g408d88af60e3268f7fad59fa393ec7e28922c435
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Aug 12 22:38:18 2021 +0200

    libcpp: Fix ICE with -Wtraditional preprocessing [PR101638]
    
    The following testcase ICEs in cpp_sys_macro_p, because cpp_sys_macro_p
    is called for a builtin macro which doesn't use node->value.macro union
    member but a different one and so dereferencing it ICEs.
    As the testcase is distilled from contemporary glibc headers, it means
    basically -Wtraditional now ICEs on almost everything.
    
    The fix can be either the patch below, return true for builtin macros,
    or we could instead return false for builtin macros, or the fix could
    be also (untested):
    --- libcpp/expr.c       2021-05-07 10:34:46.345122608 +0200
    +++ libcpp/expr.c       2021-08-12 09:54:01.837556365 +0200
    @@ -783,13 +783,13 @@ cpp_classify_number (cpp_reader *pfile,
    
           /* Traditional C only accepted the 'L' suffix.
              Suppress warning about 'LL' with -Wno-long-long.  */
    -      if (CPP_WTRADITIONAL (pfile) && ! cpp_sys_macro_p (pfile))
    +      if (CPP_WTRADITIONAL (pfile))
            {
              int u_or_i = (result & (CPP_N_UNSIGNED|CPP_N_IMAGINARY));
              int large = (result & CPP_N_WIDTH) == CPP_N_LARGE
                           && CPP_OPTION (pfile, cpp_warn_long_long);
    
    -         if (u_or_i || large)
    +         if ((u_or_i || large) && ! cpp_sys_macro_p (pfile))
                cpp_warning_with_line (pfile, large ? CPP_W_LONG_LONG : CPP_W_TRADITIONAL,
                                       virtual_location, 0,
                                       "traditional C rejects the \"%.*s\" suffix",
    The builtin macros at least currently don't add any suffixes
    or numbers -Wtraditional would like to warn about.  For floating
    point suffixes, -Wtraditional calls cpp_sys_macro_p only right
    away before emitting the warning, but in the above case the ICE
    is because cpp_sys_macro_p is called even if the number doesn't
    have any suffixes (that is I think always for builtin macros
    right now).
    
    2021-08-12  Jakub Jelinek  <jakub@redhat.com>
    
            PR preprocessor/101638
            * macro.c (cpp_sys_macro_p): Return true instead of
            crashing on builtin macros.
    
            * gcc.dg/cpp/pr101638.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/cpp/pr101638.c | 7 +++++++
 libcpp/macro.c                      | 9 +++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/cpp/pr101638.c b/gcc/testsuite/gcc.dg/cpp/pr101638.c
new file mode 100644
index 00000000000..103047320d0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/pr101638.c
@@ -0,0 +1,7 @@
+/* PR preprocessor/101638 */
+/* { dg-do preprocess } */
+/* { dg-options "-Wtraditional" } */
+
+#define foo(attr) __has_attribute(attr)
+#if foo(__deprecated__)
+#endif
diff --git a/libcpp/macro.c b/libcpp/macro.c
index 4fc5f838919..fab6779ef89 100644
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -3116,7 +3116,8 @@ cpp_get_token_with_location (cpp_reader *pfile, location_t *loc)
 
 /* Returns true if we're expanding an object-like macro that was
    defined in a system header.  Just checks the macro at the top of
-   the stack.  Used for diagnostic suppression.  */
+   the stack.  Used for diagnostic suppression.
+   Also return true for builtin macros.  */
 int
 cpp_sys_macro_p (cpp_reader *pfile)
 {
@@ -3127,7 +3128,11 @@ cpp_sys_macro_p (cpp_reader *pfile)
   else
     node = pfile->context->c.macro;
 
-  return node && node->value.macro && node->value.macro->syshdr;
+  if (!node)
+    return false;
+  if (cpp_builtin_macro_p (node))
+    return true;
+  return node->value.macro && node->value.macro->syshdr;
 }
 
 /* Read each token in, until end of the current file.  Directives are