Bug 15292 fixed pending dprintf for the CLI, but it seems they don't work properly for the MI interface.   What seems to happen is that the string to print does not get stored so when the dprintf gets activated, it has nothing to print.

Below is a session that compares pending dprintf using the CLI vs MI interfaces:

> gdb.7.7 ~/runtime-TestDSF/myapp/Debug/myapp.exe
GNU gdb (GDB) 7.7.50.20140110-cvs
(gdb)  interpreter-exec mi "-dprintf-insert -f mydll.c:1 \"hello\""
&"No source file named mydll.c.\n"
^done,bkpt={number="1",type="dprintf",disp="keep",enabled="y",addr="<PENDING>",pending="mydll.c:1",times="0",original-location="mydll.c:1"}
(gdb) dprintf mydll.c:2,"hello"
No source file named mydll.c.
Make dprintf pending on future shared library load? (y or [n]) y
Dprintf 2 (mydll.c:2,"hello") pending.
(gdb) info b
Num     Type           Disp Enb Address    What
1       dprintf        keep y   <PENDING>  mydll.c:1
2       dprintf        keep y   <PENDING>  mydll.c:2,"hello"
(gdb) b 18
Breakpoint 3 at 0x400754: file ../src/myapp.c, line 18.
(gdb) r
Starting program: /home/lmckhou/runtime-TestDSF/myapp/Debug/myapp.exe 

Breakpoint 3, main () at ../src/myapp.c:18
18           handle = dlopen("/home/lmckhou/runtime-TestDSF/myLinuxDll/Debug/libmyLinuxDll", RTLD_LAZY);
(gdb) n
Error in re-setting breakpoint 1: Format string required
19           if (!handle) {
(gdb) inf b
Num     Type           Disp Enb Address            What
1       dprintf        keep y   0x00007ffff7633560 in foo at ../src/mydll.c:1
2       dprintf        keep y   0x00007ffff7633560 in foo at ../src/mydll.c:2
        printf "hello"
3       breakpoint     keep y   0x0000000000400754 in main at ../src/myapp.c:18
        breakpoint already hit 1 time