[lldb-dev] Pending breakpoints to dlsym()ed functions

[Dmitry Antipov via lldb-dev]

On 02/15/2018 02:21 PM, Pavel Labath wrote:

> I've tried your sample, and I was indeed able to reproduce the
> problem. What makes your case special is that "sin" and "cos" are
> indirect functions (STT_GNU_IFUNC), so we have to do some extra work
> (call the resolver function) to resolve them. 

I've changed my sample to dlsym() a regular function instead of an indirect
stub, and got a breakpoint hit, but:

(lldb) attach 16196
Process 16196 stopped
* thread #1, name = 'main', stop reason = signal SIGSTOP
     frame #0: 0x0000000000400798 main`main(argc=1, argv=0x00007ffd6f662668) at main.c:16
    13  	  for (a = 0; a < DELAY + argc; a++)
    14  	    for (b = 0; b < DELAY + argc; b++)
    15  	      for (c = 0; c < DELAY + argc; c++)
-> 16  	        z += a + b + c;
    17  	  while (1)
    18  	    {
    19  	      void *handle = dlopen ("libfoo.so", RTLD_LAZY);

Executable module set to "/home/dantipov/tmp/t-dl2/main".
Architecture set to: x86_64--linux.
(lldb) breakpoint set -n foo
Breakpoint 1: no locations (pending).
WARNING:  Unable to resolve breakpoint to any actual locations.
(lldb) process continue
Process 16196 resuming
1 location added to breakpoint 1
(lldb) error: ld-linux-x86-64.so.2 0x0005d207: adding range [0x14eea-0x14f5a) which has a base that is less than the function's low PC 0x15730. Please file a bug and attach the file at the start of 
this error message
error: ld-linux-x86-64.so.2 0x0005d207: adding range [0x14f70-0x14f76) which has a base that is less than the function's low PC 0x15730. Please file a bug and attach the file at the start of this 
error message
error: ld-linux-x86-64.so.2 0x0005d268: adding range [0x14eea-0x14f5a) which has a base that is less than the function's low PC 0x15730. Please file a bug and attach the file at the start of this 
error message
error: ld-linux-x86-64.so.2 0x0005d268: adding range [0x14f70-0x14f76) which has a base that is less than the function's low PC 0x15730. Please file a bug and attach the file at the start of this 
error message
Process 16196 stopped
* thread #1, name = 'main', stop reason = breakpoint 1.1
     frame #0: 0x00007f3b1a8536f7 libfoo.so`foo(v=0.00000000000003907985046680551) at libfoo.c:6
    3   	double
    4   	foo (double v)
    5   	{
-> 6   	  return sin (v) + cos (v);
    7   	}

This seems to be an another bug, isn't it?

Dmitry

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all: libfoo.so main

libfoo.so: libfoo.c
	gcc -fPIC -O0 -g3 -shared -o libfoo.so libfoo.c -lm

main: main.c
	gcc -O0 -g3 -o main main.c -ldl

clean:
	rm -f libfoo.so main