From 4567042b5145b097c962499f26511aa5106f0e60 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Wed, 28 Feb 2018 17:53:51 +0100
Subject: Add Makefile flag to disable version sorting on C libraries without
 strverscmp

---
 README.md      |  1 +
 config.mk      | 10 +++++++++-
 man/Makefile   |  1 +
 man/feh.pre    |  3 ++-
 src/feh.h      |  7 +++++++
 src/filelist.c | 29 +++++++++++++++--------------
 6 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/README.md b/README.md
index 328897a..7848158 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,7 @@ Available flags are:
 | exif | 0 | Builtin EXIF tag display support |
 | help | 0 | include help text (refers to the manpage otherwise) |
 | stat64 | 0 | Support CIFS shares from 64bit hosts on 32bit machines |
+| verscmp | 1 | Support naturing sorting (`--version-sort`). Requires a GNU-compatible libc exposing `strverscmp` |
 | xinerama | 1 | Support Xinerama/XRandR multiscreen setups |
 
 So, by default **libcurl** and **Xinerama** are enabled, the rest is disabled.
diff --git a/config.mk b/config.mk
index 8769b1d..226c612 100644
--- a/config.mk
+++ b/config.mk
@@ -5,9 +5,10 @@ app ?= 0
 cam ?= 0
 curl ?= 1
 debug ?= 0
+exif ?= 0
 help ?= 0
+verscmp ?= 1
 xinerama ?= 1
-exif ?= 0
 
 # Prefix for all installed files
 PREFIX ?= /usr/local
@@ -63,6 +64,13 @@ ifeq (${stat64},1)
 	CFLAGS += -D_FILE_OFFSET_BITS=64
 endif
 
+ifeq (${verscmp},1)
+	CFLAGS += -DHAVE_VERSCMP
+	MAN_VERSCMP = enabled
+else
+	MAN_VERSCMP = disabled
+endif
+
 ifeq (${xinerama},1)
 	CFLAGS += -DHAVE_LIBXINERAMA
 	LDLIBS += -lXinerama
diff --git a/man/Makefile b/man/Makefile
index 65f2bc2..9209de1 100644
--- a/man/Makefile
+++ b/man/Makefile
@@ -12,6 +12,7 @@ all: ${TARGETS}
 	-e 's/\$$MAN_CURL\$$/${MAN_CURL}/' \
 	-e 's/\$$MAN_DEBUG\$$/${MAN_DEBUG}/' \
 	-e 's/\$$MAN_EXIF\$$/${MAN_EXIF}/' \
+	-e 's/\$$MAN_VERSCMP\$$/${MAN_VERSCMP}/' \
 	-e 's/\$$MAN_XINERAMA\$$/${MAN_XINERAMA}/' \
 	< ${@:.1=.pre} > $@
 
diff --git a/man/feh.pre b/man/feh.pre
index d332774..640ae3f 100644
--- a/man/feh.pre
+++ b/man/feh.pre
@@ -24,7 +24,8 @@ $VERSION$
 .
 .Pp
 .
-Compile-time switches: libcurl support $MAN_CURL$, Xinerama support
+Compile-time switches: libcurl support $MAN_CURL$, natural sorting support
+$MAN_VERSCMP$, Xinerama support
 $MAN_XINERAMA$, builtin EXIF support $MAN_EXIF$$MAN_DEBUG$
 .
 .
diff --git a/src/feh.h b/src/feh.h
index 4e7a3ff..3e0cdda 100644
--- a/src/feh.h
+++ b/src/feh.h
@@ -27,7 +27,14 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #ifndef FEH_H
 #define FEH_H
 
+/*
+ * strverscmp(3) is a GNU extension. In most supporting C libraries it
+ * requires _GNU_SOURCE to be defined.
+ */
+#ifdef HAVE_VERSCMP
 #define _GNU_SOURCE
+#endif
+
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #include <X11/Xatom.h>
diff --git a/src/filelist.c b/src/filelist.c
index 159491a..453f795 100644
--- a/src/filelist.c
+++ b/src/filelist.c
@@ -397,20 +397,26 @@ void feh_file_dirname(char *dst, feh_file * f, int maxlen)
 	dst[n] = '\0';
 }
 
-int feh_cmp_filename(void *file1, void *file2)
+#ifdef HAVE_VERSCMP
+inline int strcmp_or_strverscmp(const char *s1, const char *s2)
 {
 	if (!opt.version_sort)
-		return(strcmp(FEH_FILE(file1)->filename, FEH_FILE(file2)->filename));
+		return(strcmp(s1, s2));
 	else
-		return(strverscmp(FEH_FILE(file1)->filename, FEH_FILE(file2)->filename));
+		return(strverscmp(s1, s2));
+}
+#else
+#define strcmp_or_strverscmp strcmp
+#endif
+
+int feh_cmp_filename(void *file1, void *file2)
+{
+	return(strcmp_or_strverscmp(FEH_FILE(file1)->filename, FEH_FILE(file2)->filename));
 }
 
 int feh_cmp_name(void *file1, void *file2)
 {
-	if (!opt.version_sort)
-		return(strcmp(FEH_FILE(file1)->name, FEH_FILE(file2)->name));
-	else
-		return(strverscmp(FEH_FILE(file1)->name, FEH_FILE(file2)->name));
+	return(strcmp_or_strverscmp(FEH_FILE(file1)->name, FEH_FILE(file2)->name));
 }
 
 int feh_cmp_dirname(void *file1, void *file2)
@@ -419,13 +425,8 @@ int feh_cmp_dirname(void *file1, void *file2)
 	int cmp;
 	feh_file_dirname(dir1, FEH_FILE(file1), PATH_MAX);
 	feh_file_dirname(dir2, FEH_FILE(file2), PATH_MAX);
-	if (!opt.version_sort) {
-		if ((cmp = strcmp(dir1, dir2)) != 0)
-			return(cmp);
-	} else {
-		if ((cmp = strverscmp(dir1, dir2)) != 0)
-			return(cmp);
-	}
+	if ((cmp = strcmp_or_strverscmp(dir1, dir2)) != 0)
+		return(cmp);
 	return(feh_cmp_name(file1, file2));
 }
 
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