From f4b0d09e3f782511b99626104ca960dd5decd4b8 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Wed, 20 Nov 2019 01:22:06 -0800
Subject: Declare globals as extern in headers, and define in source file

Otherwise, each source file that includes the header gets its own
definition, and according to the C standard (C99 6.9p5):

> If an identifier declared with external linkage is used in an
> expression (other than as part of the operand of a sizeof operator
> whose result is an integer constant), somewhere in the entire
> program there shall be exactly one external definition for the
> identifier

Most compilers use the .bss section for zero data, but if it uses
.data instead, or if -Wl,--warn-common is used, this will cause a
linking error.
---
 bounce.c |  2 ++
 bounce.h | 10 +++++-----
 client.c |  3 +++
 state.c  |  3 +++
 4 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/bounce.c b/bounce.c
index 908a1cb..d4b6175 100644
--- a/bounce.c
+++ b/bounce.c
@@ -41,6 +41,8 @@
 
 #include "bounce.h"
 
+bool verbose;
+
 static void hashPass(void) {
 	char *pass = getpass("Password: ");
 	byte rand[12];
diff --git a/bounce.h b/bounce.h
index 0e12aa5..17cf5b6 100644
--- a/bounce.h
+++ b/bounce.h
@@ -110,7 +110,7 @@ static inline const char *capList(enum Cap caps) {
 	return buf;
 }
 
-bool verbose;
+extern bool verbose;
 
 void ringAlloc(size_t len);
 void ringProduce(const char *line);
@@ -134,8 +134,8 @@ void serverSend(const char *ptr, size_t len);
 void serverFormat(const char *format, ...)
 	__attribute__((format(printf, 1, 2)));
 
-char *clientPass;
-char *clientAway;
+extern char *clientPass;
+extern char *clientAway;
 struct Client *clientAlloc(struct tls *tls);
 void clientFree(struct Client *client);
 bool clientError(const struct Client *client);
@@ -146,8 +146,8 @@ void clientFormat(struct Client *client, const char *format, ...)
 size_t clientDiff(const struct Client *client);
 void clientConsume(struct Client *client);
 
-bool stateNoNames;
-enum Cap stateCaps;
+extern bool stateNoNames;
+extern enum Cap stateCaps;
 void stateLogin(
 	const char *pass, bool sasl, const char *plain,
 	const char *nick, const char *user, const char *real
diff --git a/client.c b/client.c
index d6b7b16..9ff192e 100644
--- a/client.c
+++ b/client.c
@@ -30,6 +30,9 @@
 
 #include "bounce.h"
 
+char *clientPass;
+char *clientAway;
+
 static size_t active;
 
 enum Need {
diff --git a/state.c b/state.c
index 154e16d..a661ce7 100644
--- a/state.c
+++ b/state.c
@@ -25,6 +25,9 @@
 
 #include "bounce.h"
 
+bool stateNoNames;
+enum Cap stateCaps;
+
 typedef void Handler(struct Message *msg);
 
 static void require(const struct Message *msg, bool origin, size_t len) {
-- 
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