buildsys: link installed gap executable against libgap and set SYS_DEFAULT_PATHS

Makefile.rules

@@ -300,13 +300,12 @@ ifneq (,$(findstring cygwin,$(host_os)))
 else
   ifneq (,$(findstring darwin,$(host_os)))
     GAC_CFLAGS = -fno-common
-    # HACK: we need to point to the real GAP binary, not a shell script
-    # wrapper. We can remove this hack (and once again use SYSINFO_GAP)
-    # once we get rid of the shell script wrapper
-    GAC_LDFLAGS = -bundle -bundle_loader $(SYSINFO_GAP2)
+    GAC_LDFLAGS = -bundle -bundle_loader $(SYSINFO_GAP)
+    GAC_LDFLAGS_FOR_INSTALL = -bundle -L$(libdir) -lgap
   else
     GAC_CFLAGS = -fPIC
-    GAC_LDFLAGS = -shared
+    GAC_LDFLAGS = -shared -fPIC
+    GAC_LDFLAGS_FOR_INSTALL = -shared -fPIC -L$(libdir) -lgap
   endif
 endif
 
@@ -317,7 +316,6 @@ endif
 
 # paths to gap and gac executable
 SYSINFO_GAP = $(abs_builddir)/gap
-SYSINFO_GAP2 = $(abs_builddir)/gap # HACK for bundle_loader support
 SYSINFO_GAC = $(abs_builddir)/gac
 
 
@@ -473,10 +471,19 @@ gap$(EXEEXT): libgap.la cnf/GAP-LDFLAGS cnf/GAP-LIBS cnf/GAP-OBJS build/obj/src/
 
 else
 
-# Linking rule and dependencies for the main gap executable
+# build rule for the main gap executable
 gap$(EXEEXT): $(OBJS) cnf/GAP-LDFLAGS cnf/GAP-LIBS cnf/GAP-OBJS build/obj/src/main.c.lo
 	$(QUIET_LINK)$(LINK) $(GAP_LDFLAGS) build/obj/src/main.c.lo $(GAP_LIBS) $(OBJS) -o $@
 
+# generate a modified copy of main.c for use by the `gap-install` binary
+build/main.c: src/main.c
+	@echo "#define SYS_DEFAULT_PATHS \"$(libdir)/gap;$(datarootdir)/gap\"" > $@
+	@cat $< >> $@
+
+# build rule for the gap executable used by the `install-bin` target
+build/gap-install: libgap.la cnf/GAP-LDFLAGS cnf/GAP-LIBS cnf/GAP-OBJS build/obj/build/main.c.lo
+	$(QUIET_LINK)$(LINK) $(GAP_LDFLAGS) build/obj/build/main.c.lo $(GAP_LIBS) libgap.la -o $@
+
 endif
 
 ########################################################################
@@ -572,23 +579,14 @@ install: install-bin install-doc install-gaproot install-sysinfo install-headers
 	@echo "| via support@gap-system.org or https://github.com/gap-system/gap/issues   |"
 	@echo "+--------------------------------------------------------------------------+"
 
-# the following is wrapper script which is installed by the install-bin target
-define gap_wrapper
-#!/bin/sh
-exec "$(libdir)/gap/gap" -l "$(libdir)/gap;$(datarootdir)/gap" "$$@"
-endef
-export gap_wrapper
-
-install-bin: gap
-	# install the real GAP executable as $(libdir)/gap/gap
-	$(INSTALL) -d -m 0755 $(DESTDIR)$(libdir)/gap
-	$(LTINSTALL) -s gap $(DESTDIR)$(libdir)/gap
-
-	# install a wrapper shell script invoking the real GAP executable as $(bindir)/gap
+install-bin: build/gap-install
+	# install a special build of gap with SYS_DEFAULT_PATHS set suitably
 	$(INSTALL) -d -m 0755 $(DESTDIR)$(bindir)
-	echo "$$gap_wrapper" > $(DESTDIR)$(bindir)/gap
-	chmod 0755 $(DESTDIR)$(bindir)/gap
-
+	$(LTINSTALL) -s build/gap-install $(DESTDIR)$(bindir)/gap
+	# for backwards compatibility, also install it into $(libdir)/gap
+	$(INSTALL) -d -m 0755 $(DESTDIR)$(libdir)/gap
+	$(LTINSTALL) -s build/gap-install $(DESTDIR)$(libdir)/gap/gap
+	# install gac
 	sed -e "s;@SYSINFO_GAPROOT@;$(libdir)/gap;" < $(srcdir)/cnf/gac.in > $(DESTDIR)$(bindir)/gac
 	chmod 0755 $(DESTDIR)$(bindir)/gac
 
@@ -637,8 +635,8 @@ install-gaproot: CITATION
 install-sysinfo: SYSINFO_CPPFLAGS = -I${includedir}/gap $(GAP_DEFINES)
 install-sysinfo: SYSINFO_LDFLAGS = $(ABI_CFLAGS)
 install-sysinfo: SYSINFO_GAP = $(bindir)/gap
-install-sysinfo: SYSINFO_GAP2 = $(libdir)/gap/gap
 install-sysinfo: SYSINFO_GAC = $(bindir)/gac
+install-sysinfo: GAC_LDFLAGS = $(GAC_LDFLAGS_FOR_INSTALL)
 install-sysinfo: GMP_PREFIX =
 install-sysinfo:
 	$(INSTALL) -d -m 0755 $(DESTDIR)$(libdir)/gap

src/main.c

@@ -9,18 +9,183 @@
 */
 
 #include "common.h"
+#include "sysfiles.h"
+#include "sysroots.h"
+#include "sysstr.h"
+#include "system.h"
 
 #ifdef HPCGAP
 #include "hpc/thread.h"
 #endif
 
 #include "config.h"
 
-extern int realmain(int argc, char *argv[]);
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
-int main(int argc, char *argv[])
+extern int realmain(int argc, char * argv[]);
+
+/****************************************************************************
+**
+*F * * * * * * * * * * finding location of executable * * * * * * * * * * * *
+*/
+
+#ifdef SYS_DEFAULT_PATHS
+
+static void SetupInitialGapRoot(const char * argv0)
+{
+    SySetGapRootPath(SYS_DEFAULT_PATHS);
+}
+
+#else
+
+/****************************************************************************
+**
+** The function 'find_yourself' is based on code (C) 2015 Mark Whitis, under
+** the MIT License : https://stackoverflow.com/a/34271901/928031
+*/
+static void
+find_yourself(const char * argv0, char * result, size_t resultsize)
+{
+    GAP_ASSERT(resultsize >= GAP_PATH_MAX);
+
+    char tmpbuf[GAP_PATH_MAX];
+
+    // absolute path, like '/usr/bin/gap'
+    if (argv0[0] == '/') {
+        if (realpath(argv0, result) && !access(result, F_OK)) {
+            return;    // success
+        }
+    }
+    // relative path, like 'bin/gap.sh'
+    else if (strchr(argv0, '/')) {
+        if (!getcwd(tmpbuf, sizeof(tmpbuf)))
+            return;
+        gap_strlcat(tmpbuf, "/", sizeof(tmpbuf));
+        gap_strlcat(tmpbuf, argv0, sizeof(tmpbuf));
+        if (realpath(tmpbuf, result) && !access(result, F_OK)) {
+            return;    // success
+        }
+    }
+    // executable name, like 'gap'
+    else {
+        char pathenv[GAP_PATH_MAX], *saveptr, *pathitem;
+        gap_strlcpy(pathenv, getenv("PATH"), sizeof(pathenv));
+        pathitem = strtok_r(pathenv, ":", &saveptr);
+        for (; pathitem; pathitem = strtok_r(NULL, ":", &saveptr)) {
+            gap_strlcpy(tmpbuf, pathitem, sizeof(tmpbuf));
+            gap_strlcat(tmpbuf, "/", sizeof(tmpbuf));
+            gap_strlcat(tmpbuf, argv0, sizeof(tmpbuf));
+            if (realpath(tmpbuf, result) && !access(result, F_OK)) {
+                return;    // success
+            }
+        }
+    }
+
+    *result = 0;    // reset buffer after error
+}
+
+static void SetupGAPLocation(const char * argv0, char * GAPExecLocation)
+{
+    // In the code below, we keep resetting locBuf, as some of the methods we
+    // try do not promise to leave the buffer empty on a failed return.
+    char locBuf[GAP_PATH_MAX] = "";
+    Int4 length = 0;
+
+#if defined(__APPLE__) && defined(__MACH__)
+    uint32_t len = sizeof(locBuf);
+    if (_NSGetExecutablePath(locBuf, &len) != 0) {
+        *locBuf = 0;    // reset buffer after error
+    }
+#endif
+
+    // try Linux procfs
+    if (!*locBuf) {
+        ssize_t ret = readlink("/proc/self/exe", locBuf, sizeof(locBuf));
+        if (ret < 0)
+            *locBuf = 0;    // reset buffer after error
+    }
+
+    // try FreeBSD / DragonFly BSD procfs
+    if (!*locBuf) {
+        ssize_t ret = readlink("/proc/curproc/file", locBuf, sizeof(locBuf));
+        if (ret < 0)
+            *locBuf = 0;    // reset buffer after error
+    }
+
+    // try NetBSD procfs
+    if (!*locBuf) {
+        ssize_t ret = readlink("/proc/curproc/exe", locBuf, sizeof(locBuf));
+        if (ret < 0)
+            *locBuf = 0;    // reset buffer after error
+    }
+
+    // if we are still failing, go and search the path
+    if (!*locBuf) {
+        find_yourself(argv0, locBuf, GAP_PATH_MAX);
+    }
+
+    // resolve symlinks (if present)
+    if (!realpath(locBuf, GAPExecLocation))
+        *GAPExecLocation = 0;    // reset buffer after error
+
+    // now strip the executable name off
+    length = strlen(GAPExecLocation);
+    while (length > 0 && GAPExecLocation[length] != '/') {
+        GAPExecLocation[length] = 0;
+        length--;
+    }
+}
+
+/****************************************************************************
+**
+*F  SySetInitialGapRootPaths( <string> )  . . . . .  set the root directories
+**
+**  Set up GAP's initial root paths, based on the location of the
+**  GAP executable.
+*/
+static void SySetInitialGapRootPaths(const char * GAPExecLocation)
+{
+    if (GAPExecLocation[0] != 0) {
+        // GAPExecLocation might be a subdirectory of GAP root,
+        // so we will go and search for the true GAP root.
+        // We try stepping back up to two levels.
+        char pathbuf[GAP_PATH_MAX];
+        char initgbuf[GAP_PATH_MAX];
+        strxcpy(pathbuf, GAPExecLocation, sizeof(pathbuf));
+        for (Int i = 0; i < 3; ++i) {
+            strxcpy(initgbuf, pathbuf, sizeof(initgbuf));
+            strxcat(initgbuf, "lib/init.g", sizeof(initgbuf));
+
+            if (SyIsReadableFile(initgbuf) == 0) {
+                SySetGapRootPath(pathbuf);
+                // escape from loop
+                return;
+            }
+            // try up a directory level
+            strxcat(pathbuf, "../", sizeof(pathbuf));
+        }
+    }
+
+    // Set GAP root path to current directory, if we have no other
+    // idea, and for backwards compatibility.
+    // Note that GAPExecLocation must always end with a slash.
+    SySetGapRootPath("./");
+}
+
+static void SetupInitialGapRoot(const char * argv0)
+{
+    char GAPExecLocation[GAP_PATH_MAX] = "";
+    SetupGAPLocation(argv0, GAPExecLocation);
+    SySetInitialGapRootPaths(GAPExecLocation);
+}
+#endif
+
+int main(int argc, char * argv[])
 {
     InstallBacktraceHandlers();
+    SetupInitialGapRoot(argv[0]);
 
 #ifdef HPCGAP
     RunThreadedMain(realmain, argc, argv);