diff options
Diffstat (limited to 'funtools/notes/mainlib.notes')
| -rw-r--r-- | funtools/notes/mainlib.notes | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/funtools/notes/mainlib.notes b/funtools/notes/mainlib.notes new file mode 100644 index 0000000..a1e6c2b --- /dev/null +++ b/funtools/notes/mainlib.notes @@ -0,0 +1,68 @@ +As see on Linux when running: + + saoconfig shmainlib + make + make shmainlib + setenv LD_LIBRARY_PATH . + gcc -g -o tmain -I. -I./util tmain.c libfuntoolsMainLib.a libfuntools.a -ldl -lm +or + gcc -g -o tmain -I. -I./util tmain.c libfuntools.a -ldl -lm + ./tmain -s libfuntoolsMainLib.so $S "fundisp foo[cir(512,512,.1)]" + +gives: +... +0xb7ef80f4 0xb7ef80f4 +0xb7ef80f4 +0xb7ef80f4 0xb7ef80f4 +executing: fundisp "buf:0xb7f3e008:648000[cir(512,512,.1)]" +0x8062650 +0x8062650 0x8062650 + +The hex numbers are the address of the mainlibhead list header for +mainlib records. How can this address change? + +We link tmain against either libutil.a or libfuntools.a to get the +MainLibLoad() routine. When this routine is called, it loads the +libfuntoolsMainLib.so library, and, using that library calls +funtoolsMainLibInit(). This routine makes a bunch of MainLibNew() +and uses mainlibhead in the static executable as the list head. + +Apparently, because we add -L. -lfuntools to the mklib command line: + + ./mklib -o $(PACKAGE)MainLib -L. -lfuntools $(PACKAGE)tmp/*.o; \ + +libfuntools.so is loaded as well. This has the mainlib.o module in it, +and of course, a new copy of mainlibhead. + +So, when MainLibProcess() is subsequently called, it probably comes +from the shared object, not the statically linked executable. At any +rate, it uses the mainllibhead from the shared object, which is NULL, +and therefore does not see that fundisp has been defined. + +If we don't add -L. -lfuntools to the mklib command line: + + ./mklib -o $(PACKAGE)MainLib $(PACKAGE)tmp/*.o; \ + +and remake the libfuntoolsMainLib.so file, we get an error when we try to run: + + make shmainlib + mklib: Making Linux shared library: libfuntoolsMainLib.so.1.0 + ./tmain -s libfuntoolsMainLib.so $S "fundisp foo[cir(512,512,.1)]" + can't load shared object libfuntoolsMainLib.so (./libfuntoolsMainLib.so: undefined symbol: SAOdtype) + +This is because the statically linked program does not call SAOdtype +and therefore does not have it linked in. It must come from a loaded +shared object. + +So we have to load a shared object to get funtools entry points, but we +don't want a second copy of mainlibhead ... + +Even if we separate MainLibLoad from mainlib.c and don't explicitly +load mainlib.c, we still get the wrong mainlibhead: + + nm tmain | egrep mainlib + 08062650 b mainlibhead + 08062654 b mainlibinit + 08062658 b mainlib_path + 080625f0 d mainlibundef + |