Enable extra compilation warnings

When libiphb is compiled as a part of another program that uses
'-W' parameter, it reveals potential problems in libiphb code that
'-Wall' does not show.

Note: While '-W' is still supported, nowadays '-Wextra' is preferred.

Use -Wextra when building libiphb.

[compilation] Enable extra compilation warnings. Contributes to MER#1005

configure.ac

@@ -23,7 +23,7 @@ AC_DEFINE_UNQUOTED([PRG_VERSION],[$VERSION],[Version for libiphb])
 # FIXME: DSME_LOG_ENABLE should be proper&working configure option
 #AC_DEFINE([DSME_LOG_ENABLE], [1])
 
-AC_SUBST(C_GENFLAGS, ["-pthread -g -std=c99 -Wall -Wwrite-strings -Wmissing-prototypes -Werror"])
+AC_SUBST(C_GENFLAGS, ["-pthread -g -std=c99 -Wall -Wextra -Wwrite-strings -Wmissing-prototypes -Werror"])
 AC_SUBST(C_OPTFLAGS, ["-O2 -s"])
 AC_SUBST(C_DBGFLAGS, ["-g -DDEBUG -DDSME_LOG_ENABLE"])
 

src/Makefile.am

@@ -1,7 +1,7 @@
 #
 # Generic options
 #
-AM_CFLAGS = -Wall -Wmissing-prototypes -std=c99 -Os -g -fPIC
+AM_CFLAGS = -Wall -Wextra -Wmissing-prototypes -std=c99 -Os -g -fPIC
 AM_CPPFLAGS = -D_GNU_SOURCE
 AM_LDFLAGS = -g -lrt -Wl,--as-needed
 

tests/Makefile.am

@@ -1,7 +1,7 @@
 #
 # Generic options
 #
-AM_CFLAGS = -Wall -Wmissing-prototypes -std=c99 -Os -g -fPIC
+AM_CFLAGS = -Wall -Wextra -Wmissing-prototypes -std=c99 -Os -g -fPIC
 AM_CPPFLAGS = -D_GNU_SOURCE
 AM_LDFLAGS = -g -lrt -Wl,--as-needed