epicsGetExecDir() paths relative to executable

For linux, enable softIoc to find .dbd relative to the executable
location.

The same could be done for other targets

*bsd
  may have symlink /proc/curproc/file
  fallback to sysctl() with KERN_PROC_PATHNAME

solaris
  getexecname()

mac
  _NSGetExecutablePath()

WIN32
  GetModuleFileName(NULL)

others
  out of luck...

modules/database/src/std/softIoc/softMain.cpp

@@ -62,23 +62,59 @@
 #include "epicsThread.h"
 #include "epicsExit.h"
 #include "epicsStdio.h"
+#include "epicsString.h"
 #include "dbStaticLib.h"
 #include "subRecord.h"
 #include "dbAccess.h"
 #include "asDbLib.h"
 #include "iocInit.h"
 #include "iocsh.h"
+#include "osiFileName.h"
 #include "epicsInstallDir.h"
 
 extern "C" int softIoc_registerRecordDeviceDriver(struct dbBase *pdbbase);
 
-#define DBD_FILE EPICS_BASE "/dbd/softIoc.dbd"
-#define EXIT_FILE EPICS_BASE "/db/softIocExit.db"
+#define DBD_BASE "dbd/softIoc.dbd"
+#define EXIT_BASE "db/softIocExit.db"
+#define DBD_FILE_REL "../../" DBD_BASE
+#define EXIT_FILE_REL "../../" EXIT_BASE
+#define DBD_FILE EPICS_BASE "/" DBD_BASE
+#define EXIT_FILE EPICS_BASE "/" EXIT_BASE
 
 const char *arg0;
 const char *base_dbd = DBD_FILE;
 const char *exit_db = EXIT_FILE;
 
+static void preparePath(void)
+{
+    FILE *fp;
+    char *prefix = epicsGetExecDir();
+    char *dbd, *exit;
+    if(!prefix) return;
+
+    dbd = (char*)malloc(strlen(prefix) + strlen(DBD_FILE_REL) + 1);
+    if(dbd) {
+        dbd[0] = '\0';
+        strcat(dbd, prefix);
+        strcat(dbd, DBD_FILE_REL);
+        printf("Testing '%s'\n", dbd);
+        if((fp = fopen(dbd, "rb"))!=NULL) {
+            fclose(fp);
+            base_dbd = dbd;
+        }
+    }
+
+    exit = (char*)malloc(strlen(prefix) + strlen(EXIT_FILE_REL) + 1);
+    if(exit) {
+        exit[0] = '\0';
+        strcat(exit, prefix);
+        strcat(exit, EXIT_FILE_REL);
+        if((fp = fopen(exit, "rb"))!=NULL) {
+            fclose(fp);
+            exit_db = exit;
+        }
+    }
+}
 
 static void exitSubroutine(subRecord *precord) {
     epicsExitLater((precord->a == 0.0) ? EXIT_SUCCESS : EXIT_FAILURE);
@@ -96,6 +132,7 @@ static void usage(int status) {
 
 int main(int argc, char *argv[])
 {
+    preparePath();
     char *dbd_file = const_cast<char*>(base_dbd);
     char *macros = NULL;
     char xmacro[PVNAME_STRINGSZ + 4];

modules/libcom/src/misc/unixFileName.h

@@ -14,7 +14,29 @@
 #ifndef unixFileNameH
 #define unixFileNameH
 
+#include <shareLib.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define OSI_PATH_LIST_SEPARATOR ":"
 #define OSI_PATH_SEPARATOR "/"
 
+/** Return the absolute path of the current executable.
+ @returns NULL or the path.  Caller must free()
+ */
+epicsShareFunc
+char *epicsGetExecName(void);
+
+/** Return the absolute path of the directory containing the current executable.
+ @returns NULL or the path.  Caller must free()
+ */
+epicsShareFunc
+char *epicsGetExecDir(void);
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* unixFileNameH */

modules/libcom/src/osi/Makefile

@@ -123,6 +123,7 @@ Com_SRCS += osdMonotonic.c
 Com_SRCS += osdProcess.c
 Com_SRCS += osdNetIntf.c
 Com_SRCS += osdMessageQueue.c
+Com_SRCS += osdgetexec.c
 
 Com_SRCS += devLibVME.c
 Com_SRCS += devLibVMEOSD.c

modules/libcom/src/osi/os/Linux/osdgetexec.c

@@ -0,0 +1,50 @@
+
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <limits.h>
+
+#define epicsExportSharedSymbols
+#include <osiFileName.h>
+
+char *epicsGetExecName(void)
+{
+    size_t max = PATH_MAX;
+    char *ret = NULL;
+    ssize_t n;
+
+    while(1) {
+        char *temp = realloc(ret, max);
+        if(!temp) {
+            /* we treat alloc failure as terminal */
+            free(ret);
+            ret = NULL;
+            break;
+        }
+        ret = temp;
+
+        n = readlink("/proc/self/exe", ret, max);
+        if(n < max) {
+            /* readlink() never adds a nil */
+            ret[n] = '\0';
+            break;
+        }
+
+        max += 64;
+    }
+
+    return ret;
+}
+
+char *epicsGetExecDir(void)
+{
+    char *ret = epicsGetExecName();
+    if(ret) {
+        char *sep = strrchr(ret, '/');
+        if(sep) {
+            /* nil the charactor after the / */
+            sep[1] = '\0';
+        }
+    }
+    return ret;
+}

modules/libcom/src/osi/os/WIN32/osiFileName.h

@@ -15,7 +15,29 @@
 #ifndef osiFileNameH
 #define osiFileNameH
 
+#include <shareLib.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define OSI_PATH_LIST_SEPARATOR ";"
 #define OSI_PATH_SEPARATOR "\\"
 
+/** Return the absolute path of the current executable.
+ @returns NULL or the path.  Caller must free()
+ */
+epicsShareFunc
+char *epicsGetExecName(void);
+
+/** Return the absolute path of the directory containing the current executable.
+ @returns NULL or the path.  Caller must free()
+ */
+epicsShareFunc
+char *epicsGetExecDir(void);
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* osiFileNameH */

modules/libcom/src/osi/os/cygwin32/osiFileName.h

@@ -14,7 +14,29 @@
 #ifndef osiFileNameH
 #define osiFileNameH
 
+#include <shareLib.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define OSI_PATH_LIST_SEPARATOR ";"
 #define OSI_PATH_SEPARATOR "\\"
 
+/** Return the absolute path of the current executable.
+ @returns NULL or the path.  Caller must free()
+ */
+epicsShareFunc
+char *epicsGetExecName(void);
+
+/** Return the absolute path of the directory containing the current executable.
+ @returns NULL or the path.  Caller must free()
+ */
+epicsShareFunc
+char *epicsGetExecDir(void);
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* osiFileNameH */

modules/libcom/src/osi/os/default/osdgetexec.c

@@ -0,0 +1,14 @@
+#include <stdlib.h>
+
+#define epicsExportSharedSymbols
+#include <osiFileName.h>
+
+char *epicsGetExecName(void)
+{
+    return NULL;
+}
+
+char *epicsGetExecDir(void)
+{
+    return NULL;
+}