Add DIAG_OFF_FLEX and DIAG_ON_FLEX for use in Flex scanners.

DIAG_OFF_FLEX turns off all warnings that we want to disable for
Flex-generated code due to some versions of Flex generating code that
triggers those warnings.

DIAG_ON_FLEX restores those warnings, so we do the checks for code that
*we* wrote.

Use them in .l files.

Change-Id: I613a20309a30cd4c61111a1edbe27a5d05fcbf59
Reviewed-on: https://code.wireshark.org/review/25815
Petri-Dish: Guy Harris <guy@alum.mit.edu>
Tested-by: Petri Dish Buildbot
Reviewed-by: Guy Harris <guy@alum.mit.edu>

8 files changed, 77 insertions, 53 deletions

diff --git a/epan/dfilter/scanner.l b/epan/dfilter/scanner.l
index 5f1d29df4a..63850cd178 100644
--- a/epan/dfilter/scanner.l
+++ b/epan/dfilter/scanner.l
@@ -81,13 +81,10 @@
 #include "grammar.h"
 #include "dfunctions.h"
 
-DIAG_OFF(sign-compare)
-
-#ifdef _WIN32
-/* disable Windows VC compiler warning "signed/unsigned mismatch" associated  */
-/* with YY_INPUT code generated by flex versions such as 2.5.35.              */
-#pragma warning (disable:4018)
-#endif
+/*
+ * Disable diagnostics in the code generated by Flex.
+ */
+DIAG_OFF_FLEX
 
 #define LVAL		df_lval
 #define LVAL_TYPE	stnode_t*
@@ -385,7 +382,10 @@ static void mark_lval_deprecated(const char *s);
 
 %%
 
-DIAG_ON(sign-compare)
+/*
+ * Turn diagnostics back on, so we check the code that we've written.
+ */
+DIAG_ON_FLEX
 
 static int
 simple(int token)
diff --git a/epan/dtd_preparse.l b/epan/dtd_preparse.l
index f18e44a870..669d147296 100644
--- a/epan/dtd_preparse.l
+++ b/epan/dtd_preparse.l
@@ -97,7 +97,10 @@
 #include "dtd.h"
 #include <wsutil/file_util.h>
 
-DIAG_OFF(sign-compare)
+/*
+ * Disable diagnostics in the code generated by Flex.
+ */
+DIAG_OFF_FLEX
 
 #define ECHO g_string_append(yyextra->current,yytext);
 
@@ -127,12 +130,6 @@ static const gchar* replace_entity(Dtd_PreParse_scanner_state_t* state, gchar* s
 #define YY_NO_UNISTD_H
 #endif
 
-#ifdef _WIN32
-/* disable Windows VC compiler warning "signed/unsigned mismatch" associated  */
-/* with YY_INPUT code generated by flex versions such as 2.5.35.              */
-#pragma warning (disable:4018)
-#endif
-
 /*
  * Sleazy hack to suppress compiler warnings in yy_fatal_error().
  */
@@ -212,7 +209,10 @@ newline    \n
 
 %%
 
-DIAG_ON(sign-compare)
+/*
+ * Turn diagnostics back on, so we check the code that we've written.
+ */
+DIAG_ON_FLEX
 
 static const gchar* replace_entity(Dtd_PreParse_scanner_state_t* state, gchar* entity) {
 	GString* replacement;
diff --git a/epan/radius_dict.l b/epan/radius_dict.l
index 043c91e9ad..05bfb92585 100644
--- a/epan/radius_dict.l
+++ b/epan/radius_dict.l
@@ -92,7 +92,10 @@
 #include <epan/dissectors/packet-radius.h>
 #include <wsutil/file_util.h>
 
-DIAG_OFF(sign-compare)
+/*
+ * Disable diagnostics in the code generated by Flex.
+ */
+DIAG_OFF_FLEX
 
 /*
  * See
@@ -120,12 +123,6 @@ DIAG_OFF(sign-compare)
  */
 #define YY_USER_INIT BEGIN WS_OUT;
 
-#ifdef _WIN32
-/* disable Windows VC compiler warning "signed/unsigned mismatch" associated  */
-/* with YY_INPUT code generated by flex versions such as 2.5.35.              */
-#pragma warning (disable:4018)
-#endif
-
 #define ECHO
 #define MAX_INCLUDE_DEPTH 10
 
@@ -412,7 +409,10 @@ static void add_value(Radius_scanner_state_t* state, const gchar* attrib_name, c
 
 %%
 
-DIAG_ON(sign-compare)
+/*
+ * Turn diagnostics back on, so we check the code that we've written.
+ */
+DIAG_ON_FLEX
 
 static void add_vendor(Radius_scanner_state_t* state, const gchar* name, guint32 id, guint type_octets, guint length_octets, gboolean has_flags) {
 	radius_vendor_info_t* v;
diff --git a/epan/uat_load.l b/epan/uat_load.l
index 86d5101e16..d645d0b4dc 100644
--- a/epan/uat_load.l
+++ b/epan/uat_load.l
@@ -96,13 +96,10 @@
 #include "uat-int.h"
 #include <wsutil/file_util.h>
 
-DIAG_OFF(sign-compare)
-
-#ifdef _WIN32
-/* disable Windows VC compiler warning "signed/unsigned mismatch" associated  */
-/* with YY_INPUT code generated by flex versions such as 2.5.35.              */
-#pragma warning (disable:4018)
-#endif
+/*
+ * Disable diagnostics in the code generated by Flex.
+ */
+DIAG_OFF_FLEX
 
 typedef struct {
 	uat_t* uat;
@@ -360,7 +357,10 @@ comment #[^\n]*\n
 
 %%
 
-DIAG_ON(sign-compare)
+/*
+ * Turn diagnostics back on, so we check the code that we've written.
+ */
+DIAG_ON_FLEX
 
 gboolean
 uat_load(uat_t *uat, char **errx)
diff --git a/plugins/epan/mate/mate_parser.l b/plugins/epan/mate/mate_parser.l
index b2ff7117cc..339b0cc4a2 100644
--- a/plugins/epan/mate/mate_parser.l
+++ b/plugins/epan/mate/mate_parser.l
@@ -84,13 +84,10 @@
 
 #include <wsutil/file_util.h>
 
-DIAG_OFF(sign-compare)
-
-#ifdef _WIN32
-/* disable Windows VC compiler warning "signed/unsigned mismatch" associated  */
-/* with YY_INPUT code generated by flex versions such as 2.5.35.              */
-#pragma warning (disable:4018)
-#endif
+/*
+ * Disable diagnostics in the code generated by Flex.
+ */
+DIAG_OFF_FLEX
 
 	void MateParseTrace(FILE*,char*);
 
@@ -337,7 +334,10 @@ blk_cmnt_stop  "*/"
 
 %%
 
-DIAG_ON(sign-compare)
+/*
+ * Turn diagnostics back on, so we check the code that we've written.
+ */
+DIAG_ON_FLEX
 
 extern gboolean mate_load_config(const gchar* filename, mate_config* mc) {
 	FILE *in;
diff --git a/text2pcap-scanner.l b/text2pcap-scanner.l
index 2b9e6dbab8..b4024b162d 100644
--- a/text2pcap-scanner.l
+++ b/text2pcap-scanner.l
@@ -66,7 +66,10 @@
 
 #include "text2pcap.h"
 
-DIAG_OFF(sign-compare)
+/*
+ * Disable diagnostics in the code generated by Flex.
+ */
+DIAG_OFF_FLEX
 
 /*
  * Flex (v 2.5.35) uses this symbol to "exclude" unistd.h
@@ -75,12 +78,6 @@ DIAG_OFF(sign-compare)
 #define YY_NO_UNISTD_H
 #endif
 
-#ifdef _WIN32
-/* disable Windows VC compiler warning "signed/unsigned mismatch" associated  */
-/* with YY_INPUT code generated by flex versions such as 2.5.35.              */
-#pragma warning (disable:4018)
-#endif
-
 %}
 
 hexdigit [0-9A-Fa-f]
diff --git a/ui/text_import_scanner.l b/ui/text_import_scanner.l
index 04809fc459..5e7d65048e 100644
--- a/ui/text_import_scanner.l
+++ b/ui/text_import_scanner.l
@@ -84,17 +84,16 @@
 
 #include "text_import_scanner.h"
 
-DIAG_OFF(sign-compare)
+/*
+ * Disable diagnostics in the code generated by Flex.
+ */
+DIAG_OFF_FLEX
 
 /*
  * Flex (v 2.5.35) uses this symbol to "exclude" unistd.h
  */
 #ifdef _WIN32
 #  define YY_NO_UNISTD_H
-
-   /* disable Windows VC compiler warning "signed/unsigned mismatch" associated  */
-   /* with YY_INPUT code generated by flex versions such as 2.5.35.              */
-#  pragma warning (disable:4018)
 #endif
 
 /*
diff --git a/ws_diag_control.h b/ws_diag_control.h
index 459a18a9af..155c143077 100644
--- a/ws_diag_control.h
+++ b/ws_diag_control.h
@@ -22,9 +22,16 @@ extern "C" {
 #define XSTRINGIFY(x) #x
 
 /*
- *	Macros for controlling warnings in GCC >= 4.2 and clang >= 2.8
+ *	Macros for controlling warnings in various compilers.
  */
 #define DIAG_JOINSTR(x,y) XSTRINGIFY(x ## y)
+
+/*
+ * XXX - this is only for GCC or GCC-compatible compilers, and we only use
+ * it to have a macro that takes a warning as an argument and turns it
+ * off in the appropriate fashion for Clang and GCC; it should only be
+ * used internally in this header.
+ */
 #define DIAG_DO_PRAGMA(x) _Pragma (#x)
 
 #if defined(__clang__)
@@ -84,6 +91,27 @@ extern "C" {
 #endif
 
 /*
+ * Suppress complaints about conversion of size_t to int and about
+ * signed vs. unsigned comparison.
+ *
+ * XXX - this is done solely to squelch complaints from code generated
+ * by Flex, but newer versions of Flex might fix the code; can we
+ * check the version of Flex and suppress only the checks that code
+ * generated by that version of Flex triggers?
+ */
+#if defined(_MSC_VER)
+  #define DIAG_OFF_FLEX \
+    __pragma(warning(push)) \
+    __pragma(warning(disable:4018))
+  #define DIAG_ON_FLEX	__pragma(warning(pop))
+#else
+  #define DIAG_OFF_FLEX \
+    DIAG_OFF(sign-compare)
+  #define DIAG_ON_FLEX \
+    DIAG_ON(sign-compare)
+#endif
+
+/*
  *	For dealing with APIs which are only deprecated in macOS (like the
  *	OpenSSL and MIT/Heimdal Kerberos APIs).
  *