> On 10 October 2017 at 08:54, Jiang Biao <jiang.bi...@zte.com.cn> wrote:
> > When adding a function declaration in a .c file without extern > >keywork decoration, checkpatch.pl will report *externs should be > > avoided in .c files* false error. This patch fixes the bug. > > I don't think this is a bug. "extern int foo(void);" and > "int foo(void);" have the same effect: they declare a function > prototype that can be called from outside the file. > We don't want to permit that in QEMU. Either: > (1) the function is for use only within this file: the > declaration should be "static int foo(void);" > (2) the function is for use by other files too: the > declaration should be in a header file, not a .c file, > so the other files can use it > > Do you have an example of code where this warning is a problem? Hi Peter, I understand external functions should be put in header files. But there is some rare exceptions, take the code segment in tcg/mips/tcg-target.inc.c for example, #if TCG_TARGET_REG_BITS == 32 # define LO_OFF (MIPS_BE * 4) # define HI_OFF (4 - LO_OFF) #else /* To assert at compile-time that these values are never used for TCG_TARGET_REG_BITS == 64. */ /* extern */ int link_error(void); # define LO_OFF link_error() # define HI_OFF link_error() #endif In this case, the external funciton is just used to assert at complie-time. If I make a patch to delete the commented out extern before *int link_error()*, the checkpatch.pl will complain the *externs should be avoided in .c files* error. The same usage can also be found in tcg/tcg-op.c, /* Reduce the number of ifdefs below. This assumes that all uses of TCGV_HIGH and TCGV_LOW are properly protected by a conditional that the compiler can eliminate. */ #if TCG_TARGET_REG_BITS == 64 extern TCGv_i32 TCGV_LOW_link_error(TCGv_i64); extern TCGv_i32 TCGV_HIGH_link_error(TCGv_i64); #define TCGV_LOW TCGV_LOW_link_error #define TCGV_HIGH TCGV_HIGH_link_error #endif I'm not sure if the checkpatch.pl should take these case into consideration. :) Thanks. Regards.
