configure/getprogname: fix handling and use __progname too

1. fix the handling of the fallbacks in getprogname
   i.e. actually use the fallback
2. add a check for __progname too

See #35

compat/getprogname.c

@@ -16,7 +16,19 @@
 
 #include "../config.h"
 
-#if HAVE_PROGRAM_INVOCATION_SHORT_NAME
+#if HAVE___PROGNAME
+
+#include <stddef.h>
+
+extern char *__progname;
+
+const char *
+getprogname(void)
+{
+	return __progname;
+}
+
+#elif HAVE_PROGRAM_INVOCATION_SHORT_NAME
 
 #include <errno.h>
 
@@ -29,7 +41,7 @@ getprogname(void)
 }
 
 #else
-
+# warning Found no way to get the program name, will use "gmid" for all utilities.
 const char *
 getprogname(void)
 {

configure

@@ -287,21 +287,23 @@ if [ ${HAVE_ENDIAN_H} -eq 0 -a \
 	exit 1
 fi
 
+runtest getprogname	GETPROGNAME	|| \
+runtest __progname	__PROGNAME	|| \
+runtest program_invocation_short_name PROGRAM_INVOCATION_SHORT_NAME -D_GNU_SOURCE || true
+
 runtest arc4random	ARC4RANDOM	|| true
 runtest arc4random_buf	ARC4RANDOM_BUF	|| true
 runtest err		ERR		|| true
 runtest explicit_bzero	EXPLICIT_BZERO	|| true
 runtest freezero	FREEZERO	|| true
 runtest getdtablecount	GETDTABLECOUNT	|| true
 runtest getdtablesize	GETDTABLESIZE	|| true
-runtest getprogname	GETPROGNAME	|| true
 runtest imsg		IMSG		"" -lutil libimsg || true
 runtest landlock	LANDLOCK	|| true
 runtest libevent	LIBEVENT	"" -levent libevent_core|| true
 runtest memmem		MEMMEM		-D_GNU_SOURCE || true
 runtest openssl		OPENSSL		"" '-lcrypto -lssl' 'libcrypto libssl' || true
 runtest pr_set_name	PR_SET_NAME	|| true
-runtest program_invocation_short_name PROGRAM_INVOCATION_SHORT_NAME -D_GNU_SOURCE || true
 runtest queue_h		QUEUE_H		|| true
 runtest reallocarray	REALLOCARRAY	-D_OPENBSD_SOURCE	|| true
 runtest recallocarray	RECALLOCARRAY	|| true
@@ -448,6 +450,9 @@ cat <<__HEREDOC__
 # define SYSCONFDIR		"${SYSCONFDIR}"
 #endif
 
+#define HAVE___PROGNAME		${HAVE___PROGNAME:-0}
+#define HAVE_PROGRAM_INVOCATION_SHORT_NAME ${HAVE_PROGRAM_INVOCATION_SHORT_NAME:-0}
+
 __HEREDOC__
 
 if [ ${HAVE_ENDIAN_H} -eq 1 ]; then

have/Makefile

@@ -5,6 +5,7 @@ DISTFILES =	ASN1_time_parse.c \
 		SSL_CTX_load_verify_mem.c \
 		SSL_CTX_use_certificate_chain_mem.c \
 		X509_LOOKUP_mem.c \
+		__progname.c \
 		arc4random.c \
 		arc4random_buf.c \
 		endian_h.c \

have/__progname.c

@@ -0,0 +1,11 @@
+/* public domain */
+
+#include <stdio.h>
+
+extern const char *__progname;
+
+int
+main(void)
+{
+	puts(__progname);
+}