diff --git a/build-package.sh b/build-package.sh
index 2f419888a..e5e63725a 100755
--- a/build-package.sh
+++ b/build-package.sh
@@ -328,6 +328,7 @@ termux_step_setup_variables() {
 	TERMUX_PKG_MAINTAINER="Fredrik Fornwall @fornwall"
 	TERMUX_PKG_CLANG=yes # does nothing for cmake based packages. clang is chosen by cmake
 	TERMUX_PKG_FORCE_CMAKE=no # if the package has autotools as well as cmake, then set this to prefer cmake
+	TERMUX_PKG_HAS_DEBUG=yes # set to no if debug build doesn't exist or doesn't work, for example for python based packages
 
 	unset CFLAGS CPPFLAGS LDFLAGS CXXFLAGS
 }
@@ -393,7 +394,12 @@ termux_step_start_build() {
 	fi
 
 	if [ "$TERMUX_DEBUG" == "true" ]; then
-		DEBUG="-dbg"
+		if [ "$TERMUX_PKG_HAS_DEBUG" == "yes" ]; then
+			DEBUG="-dbg"
+		else
+			echo "Skipping building debug build for $TERMUX_PKG_NAME"
+			exit 0
+		fi
 	else
 		DEBUG=""
 	fi
@@ -405,6 +411,8 @@ termux_step_start_build() {
 			echo "$TERMUX_PKG_NAME@$TERMUX_PKG_FULLVERSION built - skipping (rm /data/data/.built-packages/$TERMUX_PKG_NAME to force rebuild)"
 			exit 0
 		fi
+	else
+		export TERMUX_PKG_REPLACES=${TERMUX_PKG_NAME}
 	fi
 
 	# Cleanup old state:
@@ -758,9 +766,13 @@ termux_step_setup_toolchain() {
 # Apply all *.patch files for the package. Not to be overridden by packages.
 termux_step_patch_package() {
 	cd "$TERMUX_PKG_SRCDIR"
+	local DEBUG_PATCHES=""
+	if [ "$TERMUX_DEBUG" == "true" ] && [ -f $TERMUX_PKG_BUILDER_DIR/*.patch.debug ] ; then
+		DEBUG_PATCHES="$(ls $TERMUX_PKG_BUILDER_DIR/*.patch.debug)"
+	fi
 	# Suffix patch with ".patch32" or ".patch64" to only apply for these bitnesses:
 	shopt -s nullglob
-	for patch in $TERMUX_PKG_BUILDER_DIR/*.patch{$TERMUX_ARCH_BITS,}; do
+	for patch in $TERMUX_PKG_BUILDER_DIR/*.patch{$TERMUX_ARCH_BITS,} $DEBUG_PATCHES; do
 		test -f "$patch" && sed "s%\@TERMUX_PREFIX\@%${TERMUX_PREFIX}%g" "$patch" | \
 			sed "s%\@TERMUX_HOME\@%${TERMUX_ANDROID_HOME}%g" | \
 			patch --silent -p1
diff --git a/packages/aapt/build.sh b/packages/aapt/build.sh
index 4373c1266..a739db828 100644
--- a/packages/aapt/build.sh
+++ b/packages/aapt/build.sh
@@ -85,7 +85,17 @@ termux_step_make_install () {
 		socket_network_client_unix.c \
 		sockets_unix.o \
 		str_parms.c"
-	$CC $CFLAGS \
+	# -D_FORTIFY_SOURCE=2 makes debug build fail with:
+	# In file included from process_name.c:29:
+	# /data/data/com.termux/files/usr/include/aosp/cutils/properties.h:116:45: error: expected identifier
+	# __errordecl(__property_get_too_small_error, "property_get() called with too small of a buffer");
+	#                                               ^
+	# /data/data/com.termux/files/usr/include/aosp/cutils/properties.h:119:5: error: static declaration of 'property_get' follows non-static declaration
+	# int property_get(const char *key, char *value, const char *default_value) {
+	#       ^
+	# /data/data/com.termux/files/usr/include/aosp/cutils/properties.h:46:5: note: previous declaration is here
+	# int property_get(const char *key, char *value, const char *default_value);
+	$CC ${CFLAGS/-D_FORTIFY_SOURCE=2/} \
 		-Dchar16_t=uint16_t \
 		-std=c11 \
 		-isystem $AOSP_INCLUDE_DIR \
diff --git a/packages/alpine/imap-src-mtest-mtest.c.patch b/packages/alpine/imap-src-mtest-mtest.c.patch
new file mode 100644
index 000000000..4c2b7fc2f
--- /dev/null
+++ b/packages/alpine/imap-src-mtest-mtest.c.patch
@@ -0,0 +1,10 @@
+--- ./imap/src/mtest/mtest.c	2018-03-21 20:56:14.145999441 +0000
++++ ../mtest.c	2018-03-21 21:23:34.179966620 +0000
+@@ -34,6 +34,7 @@
+ #include <signal.h>
+ #include "c-client.h"
+ #include "imap4r1.h"
++#include "../../include/getpass.h"
+ 
+ /* Excellent reasons to hate ifdefs, and why my real code never uses them */
+ 
diff --git a/packages/asciinema/build.sh b/packages/asciinema/build.sh
index 29b9735e2..3296936bf 100644
--- a/packages/asciinema/build.sh
+++ b/packages/asciinema/build.sh
@@ -5,6 +5,7 @@ TERMUX_PKG_SHA256=7087b247dae36d04821197bc14ebd4248049592b299c9878d8953c025ac802
 TERMUX_PKG_SRCURL=https://github.com/asciinema/asciinema/archive/v${TERMUX_PKG_VERSION}.tar.gz
 TERMUX_PKG_BUILD_IN_SRC=yes
 TERMUX_PKG_PLATFORM_INDEPENDENT=yes
+TERMUX_PKG_HAS_DEBUG=no
 # ncurses-utils for tput which asciinema uses:
 TERMUX_PKG_DEPENDS="python, ncurses-utils"
 
diff --git a/packages/cboard/build.sh b/packages/cboard/build.sh
index c9b83f6bc..499e7048b 100644
--- a/packages/cboard/build.sh
+++ b/packages/cboard/build.sh
@@ -9,4 +9,10 @@ TERMUX_PKG_DEPENDS="libandroid-support,libandroid-glob,gnuchess, ncurses, ncurse
 termux_step_pre_configure () {
 	CFLAGS+=" -DLINE_MAX=_POSIX2_LINE_MAX"
 	LDFLAGS+=" -landroid-glob"
+	if [ "$TERMUX_DEBUG" == "true" ]; then
+		# When doing debug build, -D_FORTIFY_SOURCE=2 gives this error:
+		# /home/builder/.termux-build/cboard/src/libchess/pgn.c:2235:33: error: 'umask' called with invalid mode
+		# mode = umask(600);
+		export CFLAGS=${CFLAGS/-D_FORTIFY_SOURCE=2/}
+	fi
 }
diff --git a/packages/dropbear/libtomcrypt-src-headers-tomcrypt_cfg.h.patch.debug b/packages/dropbear/libtomcrypt-src-headers-tomcrypt_cfg.h.patch.debug
new file mode 100644
index 000000000..9768814cb
--- /dev/null
+++ b/packages/dropbear/libtomcrypt-src-headers-tomcrypt_cfg.h.patch.debug
@@ -0,0 +1,14 @@
+--- ./libtomcrypt/src/headers/tomcrypt_cfg.h	2017-05-18 14:47:02.000000000 +0000
++++ ../tomcrypt_cfg.h	2018-03-17 08:49:37.958092137 +0000
+@@ -35,9 +35,9 @@
+ LTC_EXPORT clock_t LTC_CALL XCLOCK(void);
+ 
+ /* various other functions */
+-LTC_EXPORT void * LTC_CALL XMEMCPY(void *dest, const void *src, size_t n);
++LTC_EXPORT void * LTC_CALL __attribute__((overloadable)) XMEMCPY(void *dest, const void *src, size_t n);
+ LTC_EXPORT int   LTC_CALL XMEMCMP(const void *s1, const void *s2, size_t n);
+-LTC_EXPORT void * LTC_CALL XMEMSET(void *s, int c, size_t n);
++LTC_EXPORT void * LTC_CALL __attribute__((overloadable)) XMEMSET(void *s, int c, size_t n);
+ 
+ LTC_EXPORT int   LTC_CALL XSTRCMP(const char *s1, const char *s2);
+ 
diff --git a/packages/expect/exp_strf.c.patch.debug b/packages/expect/exp_strf.c.patch.debug
new file mode 100644
index 000000000..ad3cf0a66
--- /dev/null
+++ b/packages/expect/exp_strf.c.patch.debug
@@ -0,0 +1,11 @@
+--- ./exp_strf.c	2000-01-06 23:22:05.000000000 +0000
++++ ../exp_strf.c	2018-03-22 19:58:34.428090961 +0000
+@@ -99,7 +99,7 @@
+ #else
+ 
+ #ifndef strchr
+-extern char *strchr(const char *str, int ch);
++extern char __attribute__((overloadable)) *strchr(const char *str, int ch);
+ #endif
+ 
+ extern char *getenv(const char *v);
diff --git a/packages/gdb/readline-histlib.h.patch.debug b/packages/gdb/readline-histlib.h.patch.debug
new file mode 100644
index 000000000..7561da6b4
--- /dev/null
+++ b/packages/gdb/readline-histlib.h.patch.debug
@@ -0,0 +1,11 @@
+--- ./readline/histlib.h	2017-06-04 15:51:27.000000000 +0000
++++ ../histlib.h	2018-03-21 15:09:37.286670845 +0000
+@@ -52,7 +52,7 @@
+ 
+ #ifndef member
+ #  ifndef strchr
+-extern char *strchr ();
++extern char __attribute__((overloadable)) *strchr ();
+ #  endif
+ #define member(c, s) ((c) ? ((char *)strchr ((s), (c)) != (char *)NULL) : 0)
+ #endif
diff --git a/packages/gettext/gettext-runtime-intl-dcigettext.c.patch.debug b/packages/gettext/gettext-runtime-intl-dcigettext.c.patch.debug
new file mode 100644
index 000000000..5ac393a60
--- /dev/null
+++ b/packages/gettext/gettext-runtime-intl-dcigettext.c.patch.debug
@@ -0,0 +1,11 @@
+--- ./gettext-runtime/intl/dcigettext.c	2016-05-19 06:49:42.000000000 +0000
++++ ../dcigettext.c	2018-03-22 06:18:22.714946338 +0000
+@@ -144,7 +144,7 @@
+ #  if VMS
+ #   define getcwd(buf, max) (getcwd) (buf, max, 0)
+ #  else
+-char *getcwd ();
++char __attribute__((overloadable)) *getcwd ();
+ #  endif
+ # endif
+ # ifndef HAVE_STPCPY
diff --git a/packages/gnuit/tilde.c-history.c.patch.debug b/packages/gnuit/tilde.c-history.c.patch.debug
new file mode 100644
index 000000000..9593e8dad
--- /dev/null
+++ b/packages/gnuit/tilde.c-history.c.patch.debug
@@ -0,0 +1,31 @@
+--- ./src/tilde.c	2009-02-18 02:31:26.000000000 +0000
++++ ../tilde.c	2018-03-17 21:38:36.637958669 +0000
+@@ -47,7 +47,7 @@
+ 
+ #if !defined (savestring)
+ #  ifndef strcpy
+-extern char *strcpy ();
++extern char __attribute__((overloadable)) *strcpy ();
+ #  endif
+ #define savestring(x) strcpy (xmalloc (1 + strlen (x)), (x))
+ #endif /* !savestring */
+--- ./src/history.c	2009-02-18 02:31:26.000000000 +0000
++++ ../history.c	2018-03-17 21:38:21.789964199 +0000
+@@ -61,7 +61,7 @@
+ 
+ #ifndef savestring
+ #  ifndef strcpy
+-extern char *strcpy ();
++extern char __attribute__((overloadable)) *strcpy ();
+ #  endif
+ #define savestring(x) strcpy (xmalloc (1 + strlen (x)), (x))
+ #endif
+@@ -80,7 +80,7 @@
+ 
+ #ifndef member
+ #  ifndef strchr
+-extern char *strchr ();
++extern char __attribute__((overloadable)) *strchr ();
+ #  endif
+ #define member(c, s) ((c) ? ((char *)strchr ((s), (c)) != (char *)NULL) : 0)
+ #endif
diff --git a/packages/gperf/lib-getopt.c.patch.debug b/packages/gperf/lib-getopt.c.patch.debug
new file mode 100644
index 000000000..04342faea
--- /dev/null
+++ b/packages/gperf/lib-getopt.c.patch.debug
@@ -0,0 +1,11 @@
+--- ./lib/getopt.c	2017-01-02 11:35:39.000000000 +0000
++++ ../getopt.c	2018-03-01 10:44:56.641412033 +0000
+@@ -210,7 +210,7 @@
+ }
+ 
+ extern int strcmp (const char *, const char *);
+-extern size_t strlen (const char *);
++extern size_t __attribute__((overloadable)) strlen (const char *);
+ 
+ #endif /* not __GNU_LIBRARY__ */
+ 
diff --git a/packages/inetutils/telnet-commands.c.patch.debug b/packages/inetutils/telnet-commands.c.patch.debug
new file mode 100644
index 000000000..88f5b4ea6
--- /dev/null
+++ b/packages/inetutils/telnet-commands.c.patch.debug
@@ -0,0 +1,20 @@
+--- ./telnet/commands.c	2015-03-31 15:40:50.000000000 +0000
++++ ../commands.c	2018-03-21 15:24:39.867877463 +0000
+@@ -1584,7 +1584,7 @@
+ 	 */
+ 	register char *shellp, *shellname;
+ # ifndef strrchr
+-	extern char *strrchr (const char *, int);
++	extern char __attribute__((overloadable)) *strrchr (const char *, int);
+ # endif
+ 
+ 	shellp = getenv ("SHELL");
+@@ -1881,7 +1881,7 @@
+   register char **epp, *cp;
+   register struct env_lst *ep;
+ #ifndef strchr
+-  extern char *strchr (const char *, int);
++  extern char __attribute__((overloadable)) *strchr (const char *, int);
+ #endif
+ 
+   for (epp = environ; *epp; epp++)
diff --git a/packages/lftp/build.sh b/packages/lftp/build.sh
index 509c53519..4cc0da86a 100644
--- a/packages/lftp/build.sh
+++ b/packages/lftp/build.sh
@@ -17,4 +17,9 @@ TERMUX_PKG_BUILD_DEPENDS="ncurses-dev"
 
 termux_step_pre_configure () {
 	TERMUX_PKG_EXTRA_CONFIGURE_ARGS+=" --with-zlib=$TERMUX_STANDALONE_TOOLCHAIN/sysroot/usr"
+	if [ "$TERMUX_DEBUG" == "true" ]; then
+		# When doing debug build, -D_FORTIFY_SOURCE=2 gives this error:
+		# /home/builder/.termux-build/_lib/16-aarch64-21-v3/bin/../sysroot/usr/include/bits/fortify/string.h:79:26: error: use of undeclared identifier '__USE_FORTIFY_LEVEL'
+		export CFLAGS=${CFLAGS/-D_FORTIFY_SOURCE=2/}
+	fi
 }
diff --git a/packages/libflac/build.sh b/packages/libflac/build.sh
index 225f54b85..9e183f247 100644
--- a/packages/libflac/build.sh
+++ b/packages/libflac/build.sh
@@ -5,3 +5,13 @@ TERMUX_PKG_REVISION=3
 TERMUX_PKG_SRCURL=http://downloads.xiph.org/releases/flac/flac-${TERMUX_PKG_VERSION}.tar.xz
 TERMUX_PKG_SHA256=91cfc3ed61dc40f47f050a109b08610667d73477af6ef36dcad31c31a4a8d53f
 TERMUX_PKG_DEPENDS="libogg"
+
+termux_step_pre_configure () {
+	if [ "$TERMUX_DEBUG" == "true" ]; then
+		# libflac does removes the flag "-g" from CFLAGS in the configure script
+		# Not sure why this is done but lets assume there is a good reason for it.
+		# -g3 is normally passed for a debug build in termux, -g is then removed
+		# and only "3" is left which isn't a valid option to the compiler.
+		export CFLAGS="${CFLAGS/-g3/}"
+	fi
+}
diff --git a/packages/libllvm/build.sh b/packages/libllvm/build.sh
index b3bba17ae..cc71e05be 100644
--- a/packages/libllvm/build.sh
+++ b/packages/libllvm/build.sh
@@ -45,6 +45,7 @@ TERMUX_PKG_EXTRA_CONFIGURE_ARGS="
 "
 TERMUX_PKG_FORCE_CMAKE=yes
 TERMUX_PKG_KEEP_STATIC_LIBRARIES=true
+TERMUX_PKG_HAS_DEBUG=no
 
 termux_step_post_extract_package () {
 	local CLANG_SRC_TAR=cfe-${TERMUX_PKG_VERSION}.src.tar.xz
diff --git a/packages/liblua/src-loslib.c.patch b/packages/liblua/src-loslib.c.patch
new file mode 100644
index 000000000..f35baf163
--- /dev/null
+++ b/packages/liblua/src-loslib.c.patch
@@ -0,0 +1,22 @@
+--- ./src/loslib.c	2017-11-18 15:51:35.425137997 +0000
++++ ../loslib.c	2017-11-18 16:20:36.202578294 +0000
+@@ -118,8 +118,8 @@
+ #define LUA_TMPNAMTEMPLATE	"/data/data/com.termux/files/usr/tmp/lua_XXXXXX"
+ #endif
+ 
+-#define lua_tmpnam(b,e) { \
+-        strcpy(b, LUA_TMPNAMTEMPLATE); \
++#define lua_tmpnam(b,e,s) {	       \
++        strncpy(b, LUA_TMPNAMTEMPLATE, s);   \
+         e = mkstemp(b); \
+         if (e != -1) close(e); \
+         e = (e == -1); }
+@@ -166,7 +166,7 @@
+ static int os_tmpname (lua_State *L) {
+   char buff[LUA_TMPNAMBUFSIZE];
+   int err;
+-  lua_tmpnam(buff, err);
++  lua_tmpnam(buff, err, LUA_TMPNAMBUFSIZE - 1);
+   if (err)
+     return luaL_error(L, "unable to generate a unique filename");
+   lua_pushstring(L, buff);
diff --git a/packages/mc/build.sh b/packages/mc/build.sh
index 8b1e58b8a..0f5333275 100755
--- a/packages/mc/build.sh
+++ b/packages/mc/build.sh
@@ -14,3 +14,13 @@ ac_cv_path_RUBY=$TERMUX_PREFIX/bin/ruby
 --with-ncurses-libs=$TERMUX_PREFIX/lib
 --with-screen=ncurses
 "
+
+termux_step_pre_configure() {
+	if [ "$TERMUX_DEBUG" == "true" ]; then
+		# Debug build fails with:
+		# /home/builder/.termux-build/mc/src/src/filemanager/file.c:2019:37: error: 'umask' called with invalid mode
+		# src_mode = umask (-1);
+		#                     ^
+		export CFLAGS=${CFLAGS/-D_FORTIFY_SOURCE=2/}
+	fi
+}
diff --git a/packages/nano/build.sh b/packages/nano/build.sh
index 5d348dd92..d0130578b 100644
--- a/packages/nano/build.sh
+++ b/packages/nano/build.sh
@@ -14,6 +14,11 @@ TERMUX_PKG_RM_AFTER_INSTALL="bin/rnano share/man/man1/rnano.1 share/nano/man-htm
 
 termux_step_pre_configure() {
 	LDFLAGS+=" -landroid-glob"
+	if [ "$TERMUX_DEBUG" == "true" ]; then
+		# When doing debug build, -D_FORTIFY_SOURCE=2 gives this error:
+		# /home/builder/.termux-build/_lib/16-aarch64-21-v3/bin/../sysroot/usr/include/bits/fortify/string.h:79:26: error: use of undeclared identifier '__USE_FORTIFY_LEVEL'
+		export CFLAGS=${CFLAGS/-D_FORTIFY_SOURCE=2/}
+	fi
 }
 
 termux_step_post_make_install () {
diff --git a/packages/nginx/build.sh b/packages/nginx/build.sh
index 81c1dae17..00d5e4c93 100644
--- a/packages/nginx/build.sh
+++ b/packages/nginx/build.sh
@@ -19,7 +19,7 @@ termux_step_pre_configure () {
 
 termux_step_configure () {
 	DEBUG_FLAG=""
-	test -n "$TERMUX_DEBUG" && DEBUG_FLAG="--debug"
+	test -n "$TERMUX_DEBUG" && DEBUG_FLAG="--with-debug"
 
 	./configure \
 		--prefix=$TERMUX_PREFIX \
diff --git a/packages/oathtool/build.sh b/packages/oathtool/build.sh
index 792ed1edc..e297d7020 100644
--- a/packages/oathtool/build.sh
+++ b/packages/oathtool/build.sh
@@ -5,3 +5,12 @@ TERMUX_PKG_SRCURL=http://download.savannah.nongnu.org/releases/oath-toolkit/oath
 TERMUX_PKG_SHA256=b03446fa4b549af5ebe4d35d7aba51163442d255660558cd861ebce536824aa0
 TERMUX_PKG_DEPENDS="xmlsec"
 TERMUX_PKG_EXTRA_CONFIGURE_ARGS="--disable-pam"
+
+termux_step_pre_configure () {
+	if [ "$TERMUX_DEBUG" == "true" ]; then
+		# When doing debug build, -D_FORTIFY_SOURCE=2 gives this error:
+		# /home/builder/.termux-build/oathtool/src/liboath/usersfile.c:482:46: error: 'umask' called with invalid mode
+		#       old_umask = umask (~(S_IRUSR | S_IWUSR));
+		export CFLAGS=${CFLAGS/-D_FORTIFY_SOURCE=2/}
+	fi
+}
diff --git a/packages/php/ext-fileinfo-libmagic-file.h.patch.debug b/packages/php/ext-fileinfo-libmagic-file.h.patch.debug
new file mode 100644
index 000000000..d0e543303
--- /dev/null
+++ b/packages/php/ext-fileinfo-libmagic-file.h.patch.debug
@@ -0,0 +1,15 @@
+--- ./ext/fileinfo/libmagic/file.h	2018-02-27 16:33:03.000000000 +0000
++++ ../file.h	2018-03-22 19:36:35.759933435 +0000
+@@ -511,10 +511,10 @@
+ #endif
+ 
+ #ifndef strlcpy
+-size_t strlcpy(char *, const char *, size_t);
++size_t __attribute__((overloadable)) strlcpy(char *, const char *, size_t);
+ #endif
+ #ifndef strlcat
+-size_t strlcat(char *, const char *, size_t);
++size_t __attribute__((overloadable)) strlcat(char *, const char *, size_t);
+ #endif
+ #ifndef HAVE_STRCASESTR
+ char *strcasestr(const char *, const char *);
diff --git a/packages/readline/histlib.h.patch.debug b/packages/readline/histlib.h.patch.debug
new file mode 100644
index 000000000..7b49b14dc
--- /dev/null
+++ b/packages/readline/histlib.h.patch.debug
@@ -0,0 +1,11 @@
+--- ./histlib.h	2016-04-22 15:03:20.000000000 +0000
++++ ../histlib.h	2018-03-18 19:50:23.834494092 +0000
+@@ -52,7 +52,7 @@
+ 
+ #ifndef member
+ #  ifndef strchr
+-extern char *strchr ();
++extern char __attribute__((overloadable)) *strchr ();
+ #  endif
+ #define member(c, s) ((c) ? ((char *)strchr ((s), (c)) != (char *)NULL) : 0)
+ #endif
diff --git a/packages/texlive/build.sh b/packages/texlive/build.sh
index 96d37a678..f6438d5bd 100644
--- a/packages/texlive/build.sh
+++ b/packages/texlive/build.sh
@@ -11,6 +11,7 @@ TERMUX_PKG_CONFLICTS="texlive (<< 20170524-5), texlive-bin (<< 20180414)"
 TERMUX_PKG_RECOMMENDS="texlive-tlmgr"
 TERMUX_PKG_FOLDERNAME="texlive-$_MAJOR_VERSION-texmf"
 TERMUX_PKG_PLATFORM_INDEPENDENT=yes
+TERMUX_PKG_HAS_DEBUG=no
 
 TL_FILE_LISTS="texlive-texmf.list"
 TL_ROOT=$TERMUX_PREFIX/share/texlive
diff --git a/packages/tsocks/tsocks.patch.debug b/packages/tsocks/tsocks.patch.debug
new file mode 100644
index 000000000..23329cbc6
--- /dev/null
+++ b/packages/tsocks/tsocks.patch.debug
@@ -0,0 +1,33 @@
+--- ./configure	2018-03-01 11:48:24.972390791 +0000
++++ ../configure	2018-03-01 12:17:17.702571991 +0000
+@@ -2283,7 +2283,7 @@
+ #include "confdefs.h"
+ 
+       #include <sys/poll.h>
+-      int poll($testproto);
++      int __attribute__((overloadable)) poll($testproto);
+     
+ int main() {
+ 
+--- ./tsocks.c	2018-03-01 12:18:42.778500423 +0000
++++ ../tsocks.c	2018-03-01 12:19:31.726457927 +0000
+@@ -72,7 +72,7 @@
+ void _init(void);
+ int connect(CONNECT_SIGNATURE);
+ int select(SELECT_SIGNATURE);
+-int poll(POLL_SIGNATURE);
++int __attribute__((overloadable)) poll(POLL_SIGNATURE);
+ int close(CLOSE_SIGNATURE);
+ int getpeername(GETPEERNAME_SIGNATURE);
+ #ifdef USE_SOCKS_DNS
+--- ./tsocks.c	2018-03-01 12:21:27.198354152 +0000
++++ ../tsocks.c	2018-03-01 12:21:59.098324662 +0000
+@@ -538,7 +538,7 @@
+    return(nevents);
+ }
+ 
+-int poll(POLL_SIGNATURE) {
++int __attribute__((overloadable)) poll(POLL_SIGNATURE) {
+    int nevents = 0;
+    int rc = 0, i;
+    int setevents = 0;
diff --git a/packages/units/units.h.patch.debug b/packages/units/units.h.patch.debug
new file mode 100644
index 000000000..787b216f9
--- /dev/null
+++ b/packages/units/units.h.patch.debug
@@ -0,0 +1,11 @@
+--- ./units.h	2017-02-09 21:43:12.000000000 +0000
++++ ../units.h	2018-03-21 20:22:04.544833906 +0000
+@@ -54,7 +54,7 @@
+ #  ifdef NO_STRCHR
+ #    define strchr(a,b) index((a),(b))
+ #  else
+-     char *strchr();
++     char __attribute__((overloadable)) *strchr();
+ #  endif
+ #endif /* !strchr */
+ 
diff --git a/packages/vifm/build.sh b/packages/vifm/build.sh
index 1258b1fb6..c07471180 100644
--- a/packages/vifm/build.sh
+++ b/packages/vifm/build.sh
@@ -7,4 +7,10 @@ TERMUX_PKG_DEPENDS="ncurses, file"
 
 termux_step_pre_configure() {
 	autoreconf -if
+	if [ "$TERMUX_DEBUG" == "true" ]; then
+		# Debug build fails with:
+		# /home/builder/.termux-build/vifm/src/src/fops_common.c:745:27: error: 'umask' called with invalid mode
+		#      saved_umask = umask(~0600);
+		export CFLAGS=${CFLAGS/-D_FORTIFY_SOURCE=2/}
+	fi
 }