From 2a96bc336a86b5178019e9f4880f00e65f1e9b11 Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@cryptomilk.org>
Date: Mon, 17 Feb 2020 16:33:55 +0100
Subject: [PATCH 1/7] nvim:eval: Fix enum declaration for ListLenSpecials

Instead of declaring an enum, this creates a global variable. As gcc10
uses -fno-common by default, global variables declared with the same
name more than once is not allowed anymore revealing this issue.

Each time this header is included, we define the enum name as a global
variable.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1799680
---
 src/nvim/eval/typval.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/nvim/eval/typval.h b/src/nvim/eval/typval.h
index 008453b87..5afdedff7 100644
--- a/src/nvim/eval/typval.h
+++ b/src/nvim/eval/typval.h
@@ -33,7 +33,7 @@ typedef double float_T;
 enum { DO_NOT_FREE_CNT = (INT_MAX / 2) };
 
 /// Additional values for tv_list_alloc() len argument
-enum {
+enum ListLenSpecials {
   /// List length is not known in advance
   ///
   /// To be used when there is neither a way to know how many elements will be
@@ -49,7 +49,7 @@ enum {
   ///
   /// To be used when it looks impractical to determine list length.
   kListLenMayKnow = -3,
-} ListLenSpecials;
+};
 
 /// Maximal possible value of varnumber_T variable
 #define VARNUMBER_MAX INT64_MAX
-- 
2.25.0


From 1ff3e86b44204e15e07e152f353e389bd72836d7 Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@cryptomilk.org>
Date: Mon, 17 Feb 2020 17:17:37 +0100
Subject: [PATCH 2/7] nvim:viml: Fix enum declaration of ExprParserFlags

Instead of declaring an enum, this creates a global variable. As gcc10
uses -fno-common by default, global variables declared with the same
name more than once is not allowed anymore revealing this issue.

Each time this header is included, we define the enum name as a global
variable.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1799680
---
 src/nvim/viml/parser/expressions.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/nvim/viml/parser/expressions.h b/src/nvim/viml/parser/expressions.h
index 23e172da7..838a74227 100644
--- a/src/nvim/viml/parser/expressions.h
+++ b/src/nvim/viml/parser/expressions.h
@@ -326,7 +326,7 @@ struct expr_ast_node {
   } data;
 };
 
-enum {
+enum ExprParserFlags {
   /// Allow multiple expressions in a row: e.g. for :echo
   ///
   /// Parser will still parse only one of them though.
@@ -345,7 +345,7 @@ enum {
   //     viml_expressions_parser.c, nvim_parse_expression() flags parsing
   //     alongside with its documentation and flag sets in check_parsing()
   //     function in expressions parser functional and unit tests.
-} ExprParserFlags;
+};
 
 /// AST error definition
 typedef struct {
-- 
2.25.0


From 400111a478b9f522ee98f06bda4660226961806f Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@cryptomilk.org>
Date: Mon, 17 Feb 2020 16:36:21 +0100
Subject: [PATCH 3/7] nvim: Fix enum declaration of RemapValues

Instead of declaring an enum, this creates a global variable. As gcc10
uses -fno-common by default, global variables declared with the same
name more than once is not allowed anymore revealing this issue.

Each time this header is included, we define the enum name as a global
variable.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1799680
---
 src/nvim/getchar.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/nvim/getchar.h b/src/nvim/getchar.h
index 01f60ccf4..f0b52079a 100644
--- a/src/nvim/getchar.h
+++ b/src/nvim/getchar.h
@@ -10,12 +10,12 @@
 /// Values for "noremap" argument of ins_typebuf()
 ///
 /// Also used for map->m_noremap and menu->noremap[].
-enum {
+enum RemapValues {
   REMAP_YES = 0,  ///< Allow remapping.
   REMAP_NONE = -1,  ///< No remapping.
   REMAP_SCRIPT = -2,  ///< Remap script-local mappings only.
   REMAP_SKIP = -3,  ///< No remapping for first char.
-} RemapValues;
+};
 
 // Argument for flush_buffers().
 typedef enum {
-- 
2.25.0


From f870d61a336756a71e719f89752be796fcee45ea Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@cryptomilk.org>
Date: Mon, 17 Feb 2020 16:40:37 +0100
Subject: [PATCH 4/7] nvim:msgpack: Correctly set up global
 ch_before_blocking_events

gcc10 builds with -fno-common by default. This mean you can't define
a global variable with the same name twice.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1799680
---
 src/nvim/msgpack_rpc/channel.h | 2 +-
 src/nvim/os/input.c            | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/nvim/msgpack_rpc/channel.h b/src/nvim/msgpack_rpc/channel.h
index 9ff5abdc5..90e1c7d48 100644
--- a/src/nvim/msgpack_rpc/channel.h
+++ b/src/nvim/msgpack_rpc/channel.h
@@ -15,7 +15,7 @@
 /// HACK: os/input.c drains this queue immediately before blocking for input.
 ///       Events on this queue are async-safe, but they need the resolved state
 ///       of os_inchar(), so they are processed "just-in-time".
-MultiQueue *ch_before_blocking_events;
+EXTERN MultiQueue *ch_before_blocking_events INIT(= NULL);
 
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
diff --git a/src/nvim/os/input.c b/src/nvim/os/input.c
index c1580c5fc..b466b1bef 100644
--- a/src/nvim/os/input.c
+++ b/src/nvim/os/input.c
@@ -1,6 +1,7 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
+#define EXTERN
 #include <assert.h>
 #include <string.h>
 #include <stdbool.h>
-- 
2.25.0


From 5471ef87c02fedf4b19870019e23da17e56a037f Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@cryptomilk.org>
Date: Mon, 17 Feb 2020 17:29:12 +0100
Subject: [PATCH 5/7] nvim: Correctly setup global channels

As gcc10 uses -fno-common by default, global variables declared with the
same name more than once is not allowed anymore revealing this issue.

We need to define it as extern to access it.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1799680
---
 src/nvim/channel.c | 1 -
 src/nvim/channel.h | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/nvim/channel.c b/src/nvim/channel.c
index c66a0682e..5eb29a729 100644
--- a/src/nvim/channel.c
+++ b/src/nvim/channel.c
@@ -19,7 +19,6 @@
 #include "nvim/ascii.h"
 
 static bool did_stdio = false;
-PMap(uint64_t) *channels = NULL;
 
 /// next free id for a job or rpc channel
 /// 1 is reserved for stdio channel
diff --git a/src/nvim/channel.h b/src/nvim/channel.h
index c733e276b..9d26852ce 100644
--- a/src/nvim/channel.h
+++ b/src/nvim/channel.h
@@ -85,7 +85,7 @@ struct Channel {
   bool callback_scheduled;
 };
 
-EXTERN PMap(uint64_t) *channels;
+EXTERN PMap(uint64_t) *channels INIT(= NULL);
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "channel.h.generated.h"
-- 
2.25.0


From c04cf8ab059aeddc9bc74415bceb6d9de6948dcd Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@cryptomilk.org>
Date: Mon, 17 Feb 2020 19:06:47 +0100
Subject: [PATCH 6/7] nvim:os: Include ui.h and channel.h we define EXTERN

If we define EXTERN as an emtpy macro we would duplicate the globals.
---
 src/nvim/os/input.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/nvim/os/input.c b/src/nvim/os/input.c
index b466b1bef..cc551d104 100644
--- a/src/nvim/os/input.c
+++ b/src/nvim/os/input.c
@@ -1,20 +1,24 @@
 // This is an open source non-commercial project. Dear PVS-Studio, please check
 // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
 
-#define EXTERN
 #include <assert.h>
 #include <string.h>
 #include <stdbool.h>
 
 #include <uv.h>
 
+// This needs to be included before we define EXTERN
+#include "nvim/ui.h"
+#include "nvim/msgpack_rpc/channel.h"
+
+#undef EXTERN
+#define EXTERN
 #include "nvim/api/private/defs.h"
 #include "nvim/os/input.h"
 #include "nvim/event/loop.h"
 #include "nvim/event/rstream.h"
 #include "nvim/ascii.h"
 #include "nvim/vim.h"
-#include "nvim/ui.h"
 #include "nvim/memory.h"
 #include "nvim/keymap.h"
 #include "nvim/mbyte.h"
@@ -24,7 +28,6 @@
 #include "nvim/main.h"
 #include "nvim/misc1.h"
 #include "nvim/state.h"
-#include "nvim/msgpack_rpc/channel.h"
 
 #define READ_BUFFER_SIZE 0xfff
 #define INPUT_BUFFER_SIZE (READ_BUFFER_SIZE * 4)
-- 
2.25.0


From 4ebbca53cfdba5313f86477c00536fd47993bfbb Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@cryptomilk.org>
Date: Mon, 17 Feb 2020 18:04:01 +0100
Subject: [PATCH 7/7] cmake: Check for -fno-common and use it if available

---
 CMakeLists.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index de530bb4f..7c237781c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -306,6 +306,13 @@ if(UNIX)
     add_compile_options(-fstack-protector --param ssp-buffer-size=4)
     link_libraries(-fstack-protector --param ssp-buffer-size=4)
   endif()
+
+  check_c_compiler_flag(-fno-common HAVE_FNO_COMMON)
+  if (HAVE_FNO_COMMON)
+    add_compile_options(-fno-common)
+  endif()
+endif()
+
 endif()
 
 check_c_compiler_flag(-fdiagnostics-color=auto HAS_DIAG_COLOR_FLAG)
-- 
2.25.0