我已经在fedora上下载了开源gt包的源代码，并试图在Debian上编译它。在编译过程中，instrum.c中的这段代码在标题中出现以下错误：

#define READ_CHAR(thing) \
      thing = tmp[tmpindex++];

完整的错误报告如下：

instrum.c: In function ‘load_instrument’:
instrum.c:944:13: error: lvalue required as left operand of assignment
  944 |       thing = tmp[tmpindex++];
      |             ^
instrum.c:1173:7: note: in expansion of macro ‘READ_CHAR’
 1173 |       READ_CHAR ((int8)sp->aps_parameter);
      |       ^~~~~~~~~
make[1]: *** [Makefile:335: instrum.o] Error 1
make[1]: Leaving directory '/home/classic/gt-0.4/src'
make: *** [Makefile:235: all] Error 2

sp定义的结构如下：

typedef struct {
  splen_t
    loop_start, loop_end, data_length;
  ...
  ...
  int32
    freq_scale, vibrato_delay;
  int8
    aps_parameter, sw_up, sw_down, sw_lokey, sw_hikey, sw_last;
} Sample;