From 1de7bfaf749dddf4e1e2840dbab6aee1559ace29 Mon Sep 17 00:00:00 2001
From: David Malcolm <dmalcolm@redhat.com>
Date: Fri, 7 Apr 2017 20:18:16 -0400
Subject: [PATCH 08/10] FIXME: C FE: hints for missing stdlib includes

---
 gcc/c/c-decl.c                           | 79 ++++++++++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/spellcheck-stdlib.c | 55 ++++++++++++++++++++++
 2 files changed, 134 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/spellcheck-stdlib.c

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index d19f545..91ace02 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -3998,6 +3998,77 @@ lookup_name_in_scope (tree name, struct c_scope *scope)
   return NULL_TREE;
 }
 
+/* Subroutine of suggest_missing_header::emit for handling unrecognized names
+   for some of the most common names within the C standard library.
+   Given non-NULL NAME, return the header name defining it within the C
+   standard library (without '<' and '>'), or NULL.  */
+
+static const char *
+get_c_name_hint (const char *name)
+{
+  struct std_name_hint
+  {
+    const char *name;
+    const char *header;
+  };
+  static const std_name_hint hints[] = {
+    /* <errno.h>.  */
+    {"errno", "errno.h"},
+
+    /* <stdarg.h>.  */
+    {"va_list", "stdarg.h"},
+
+    /* <stddef.h>.  */
+    {"NULL", "stddef.h"},
+    {"ptrdiff_t", "stddef.h"},
+    {"wchar_t", "stddef.h"},
+    {"size_t", "stddef.h"},
+
+    /* <stdio.h>.  */
+    {"BUFSIZ", "stdio.h"},
+    {"EOF", "stdio.h"},
+    {"FILE", "stdio.h"},
+    {"FILENAME_MAX", "stdio.h"},
+    {"fpos_t", "stdio.h"},
+    {"stderr", "stdio.h"},
+    {"stdin", "stdio.h"},
+    {"stdout", "stdio.h"}
+  };
+  const size_t num_hints = sizeof (hints) / sizeof (hints[0]);
+  for (size_t i = 0; i < num_hints; i++)
+    {
+      if (0 == strcmp (name, hints[i].name))
+	return hints[i].header;
+    }
+  /* FIXME: unify this with one in C++.  */
+  return NULL;
+}
+
+/* FIXME.  */
+
+class suggest_missing_header : public deferred_diagnostic
+{
+ public:
+  suggest_missing_header (const char *name, const char *header_hint)
+  : m_name_str (name), m_header_hint (header_hint)
+  {
+    gcc_assert (name);
+    gcc_assert (header_hint);
+  }
+
+  void emit ()
+  {
+    inform (input_location,
+	    "%<%s%> is defined in header %<<%s>%>;"
+	    " did you forget to %<#include <%s>%>?",
+	    m_name_str, m_header_hint, m_header_hint);
+  }
+
+ private:
+  const char *m_name_str;
+  const char *m_header_hint;
+};
+
 /* Look for the closest match for NAME within the currently valid
    scopes.
 
@@ -4019,6 +4090,14 @@ lookup_name_fuzzy (tree name, enum lookup_name_fuzzy_kind kind)
 {
   gcc_assert (TREE_CODE (name) == IDENTIFIER_NODE);
 
+  /* First, try some well-known names in the C standard library, in case
+     the user forgot a #include.  */
+  const char *header_hint = get_c_name_hint (IDENTIFIER_POINTER (name));
+  if (header_hint)
+    return name_hint (NULL,
+		      new suggest_missing_header (IDENTIFIER_POINTER (name),
+						  header_hint));
+
   best_match<tree, tree> bm (name);
 
   /* Look within currently valid scopes.  */
diff --git a/gcc/testsuite/gcc.dg/spellcheck-stdlib.c b/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
new file mode 100644
index 0000000..85a21c3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
@@ -0,0 +1,55 @@
+/* Missing <stddef.h>.  */
+
+void *ptr = NULL; /* { dg-error "'NULL' undeclared here" } */
+/* { dg-message "'NULL' is defined in header '<stddef.h>'; did you forget to '#include <stddef.h>'?" "" { target *-*-* } .-1 } */
+
+ptrdiff_t pd; /* { dg-error "unknown type name 'ptrdiff_t'" } */
+/* { dg-message "'ptrdiff_t' is defined in header '<stddef.h>'; did you forget to '#include <stddef.h>'?" "" { target *-*-* } .-1 } */
+
+wchar_t wc; /* { dg-error "unknown type name 'wchar_t'" } */
+/* { dg-message "'wchar_t' is defined in header '<stddef.h>'; did you forget to '#include <stddef.h>'?" "" { target *-*-* } .-1 } */
+
+size_t sz; /* { dg-error "unknown type name 'size_t'" } */
+/* { dg-message "'size_t' is defined in header '<stddef.h>'; did you forget to '#include <stddef.h>'?" "" { target *-*-* } .-1 } */
+
+/* Missing <stdio.h>.  */
+
+void test_stdio_h (void)
+{
+  FILE *f; /* { dg-error "unknown type name 'FILE'" } */
+  /* { dg-message "'FILE' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?" "" { target *-*-* } .-1 } */
+
+  char buf[BUFSIZ]; /* { dg-error "'BUFSIZ' undeclared" } */
+  /* { dg-message "'BUFSIZ' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?" "" { target *-*-* } .-1 } */
+
+  char buf2[FILENAME_MAX]; /* { dg-error "'FILENAME_MAX' undeclared" } */
+  /* { dg-message "'FILENAME_MAX' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?" "" { target *-*-* } .-1 } */
+
+  stderr; /* { dg-error "'stderr' undeclared" } */
+  /* { dg-message "'stderr' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?" "" { target *-*-* } .-1 } */
+
+  stdin; /* { dg-error "'stdin' undeclared" } */
+  /* { dg-message "'stdin' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?" "" { target *-*-* } .-1 } */
+
+  stdout; /* { dg-error "'stdout' undeclared" } */
+  /* { dg-message "'stdout' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?" "" { target *-*-* } .-1 } */
+
+  EOF; /* { dg-error "'EOF' undeclared" } */
+  /* { dg-message "'EOF' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?" "" { target *-*-* } .-1 } */
+}
+
+/* Missing <errno.h>.  */
+
+int test_errno_h (void)
+{
+  return errno; /* { dg-error "'errno' undeclared" } */
+  /* { dg-message "'errno' is defined in header '<errno.h>'; did you forget to '#include <errno.h>'?" "" { target *-*-* } .-1 } */
+}
+
+/* Missing <stdarg.h>.  */
+
+void test_stdarg_h (void)
+{
+  va_list ap; /* { dg-error "unknown type name 'va_list'" } */
+  /* { dg-message "'va_list' is defined in header '<stdarg.h>'; did you forget to '#include <stdarg.h>'?" "" { target *-*-* } .-1 } */
+}
-- 
1.8.5.3