.\Objects\STM32F746NGH6-DISCOVERY.axf: Error: L6971E: gui_x_rte.o(.data) type RW incompatible with lcdconf.o(.ARM.__AT_0x20000000) type ZI in er RW_IRAM2.

L6971E
<objname>(<secname>) type <type> incompatible with <prevobj>(<prevname>) type <prevtype> in er <ername>.
You might see this message when placing __at sections with a scatter file. For example, the following code in main.c and the related scatter file gives this error:
int variable __attribute__((at(0x200000)));
LR1 0x0000 0x20000
{
    ER1 0x0 0x2000
    {
        *(+RO)
    }
    ER2 0x8000 0x2000
    {
        main.o
    }
    RAM 0x200000 (0x1FF00-0x2000)
    {
        *(+RW, +ZI)
    }
}
The variable has the type ZI, and the linker attempts to place it at address 0x200000. However, this address is reserved for RW sections by the scatter file. This produces the error:
Error: L6971E: stdio_streams.o(.data) type RW incompatible with main.o(.ARM.__AT_0x00200000) type ZI in er RAM.
To fix this change the address in your source code, for example:
int variable __attribute__((at(0x210000)));

               AREA   |.ARM.__AT_0x2000000|,DATA,READWRITE
                                  EXPORT lcdconf
lcdconf     space 20

extern char lcdconf[20];

; *************************************************************
; *** Scatter-Loading Description File generated by uVision ***
; *************************************************************

LR_IROM1 0x08000000 0x00100000  {   ; load region size_region
  ER_IROM1 0x08000000 0x00100000  { ; load address = execution address
   *.o (RESET, +First)
   *(InRoot$$Sections)
   .ANY (+RO)
  }
  RW_IRAM1 0x20010000 0x00040000  { ; RW data
   .ANY (+RW +ZI)
  }
  RW_IRAM2 0x20000000 0x00010000  {
   *GUI_CM4F_L.lib (+RO +ZI +RW)
    GUI_X_RTE.o (+RO +ZI +RW)
    GUIConf.o (+RO +ZI +RW)
   .ANY (+RW +ZI)
  }
}