-Wincompatible-library-redeclaration

[nickdesaulniers]

Testing ARCH=arm allyesconfig on stable 6.3 and linux-next with ToT LLVM, after running into #1855 I then hit:

CC      scripts/mod/devicetable-offsets.s
In file included from scripts/mod/devicetable-offsets.c:3:
In file included from ./include/linux/mod_devicetable.h:14:
In file included from ./include/linux/uuid.h:11:
In file included from ./include/linux/string.h:20:
./arch/arm/include/asm/string.h:20:15: error: incompatible redeclaration of library function 'memcpy' [-Werror,-Wincompatible-library-redeclaration]
extern void * memcpy(void *, const void *, __kernel_size_t);
              ^
./arch/arm/include/asm/string.h:20:15: note: 'memcpy' is a builtin with type 'void *(void *, const void *, unsigned long)'
./arch/arm/include/asm/string.h:24:15: error: incompatible redeclaration of library function 'memmove' [-Werror,-Wincompatible-library-redeclaration]
extern void * memmove(void *, const void *, __kernel_size_t);
              ^
./arch/arm/include/asm/string.h:24:15: note: 'memmove' is a builtin with type 'void *(void *, const void *, unsigned long)'
./arch/arm/include/asm/string.h:28:15: error: incompatible redeclaration of library function 'memchr' [-Werror,-Wincompatible-library-redeclaration]
extern void * memchr(const void *, int, __kernel_size_t);
              ^
./arch/arm/include/asm/string.h:28:15: note: 'memchr' is a builtin with type 'void *(const void *, int, unsigned long)'
./arch/arm/include/asm/string.h:31:15: error: incompatible redeclaration of library function 'memset' [-Werror,-Wincompatible-library-redeclaration]
extern void * memset(void *, int, __kernel_size_t);
              ^
./arch/arm/include/asm/string.h:31:15: note: 'memset' is a builtin with type 'void *(void *, int, unsigned long)'
In file included from scripts/mod/devicetable-offsets.c:3:
In file included from ./include/linux/mod_devicetable.h:14:
In file included from ./include/linux/uuid.h:11:
./include/linux/string.h:26:15: error: incompatible redeclaration of library function 'strncpy' [-Werror,-Wincompatible-library-redeclaration]
extern char * strncpy(char *,const char *, __kernel_size_t);
              ^
./include/linux/string.h:26:15: note: 'strncpy' is a builtin with type 'char *(char *, const char *, unsigned long)'
./include/linux/string.h:29:8: error: incompatible redeclaration of library function 'strlcpy' [-Werror,-Wincompatible-library-redeclaration]
size_t strlcpy(char *, const char *, size_t);
       ^
./include/linux/string.h:29:8: note: 'strlcpy' is a builtin with type 'unsigned long (char *, const char *, unsigned long)'
./include/linux/string.h:42:15: error: incompatible redeclaration of library function 'strncat' [-Werror,-Wincompatible-library-redeclaration]
extern char * strncat(char *, const char *, __kernel_size_t);
              ^
./include/linux/string.h:42:15: note: 'strncat' is a builtin with type 'char *(char *, const char *, unsigned long)'
./include/linux/string.h:45:15: error: incompatible redeclaration of library function 'strlcat' [-Werror,-Wincompatible-library-redeclaration]
extern size_t strlcat(char *, const char *, __kernel_size_t);
              ^
./include/linux/string.h:45:15: note: 'strlcat' is a builtin with type 'unsigned long (char *, const char *, unsigned long)'
./include/linux/string.h:51:12: error: incompatible redeclaration of library function 'strncmp' [-Werror,-Wincompatible-library-redeclaration]
extern int strncmp(const char *,const char *,__kernel_size_t);
           ^
./include/linux/string.h:51:12: note: 'strncmp' is a builtin with type 'int (const char *, const char *, unsigned long)'
./include/linux/string.h:57:12: error: incompatible redeclaration of library function 'strncasecmp' [-Werror,-Wincompatible-library-redeclaration]
extern int strncasecmp(const char *s1, const char *s2, size_t n);
           ^
./include/linux/string.h:57:12: note: 'strncasecmp' is a builtin with type 'int (const char *, const char *, unsigned long)'
./include/linux/string.h:88:24: error: incompatible redeclaration of library function 'strlen' [-Werror,-Wincompatible-library-redeclaration]
extern __kernel_size_t strlen(const char *);
                       ^
./include/linux/string.h:88:24: note: 'strlen' is a builtin with type 'unsigned long (const char *)'
./include/linux/string.h:100:24: error: incompatible redeclaration of library function 'strspn' [-Werror,-Wincompatible-library-redeclaration]
extern __kernel_size_t strspn(const char *,const char *);
                       ^
./include/linux/string.h:100:24: note: 'strspn' is a builtin with type 'unsigned long (const char *, const char *)'
./include/linux/string.h:103:24: error: incompatible redeclaration of library function 'strcspn' [-Werror,-Wincompatible-library-redeclaration]
extern __kernel_size_t strcspn(const char *,const char *);
                       ^
./include/linux/string.h:103:24: note: 'strcspn' is a builtin with type 'unsigned long (const char *, const char *)'
./include/linux/string.h:156:12: error: incompatible redeclaration of library function 'memcmp' [-Werror,-Wincompatible-library-redeclaration]
extern int memcmp(const void *,const void *,__kernel_size_t);
           ^
./include/linux/string.h:156:12: note: 'memcmp' is a builtin with type 'int (const void *, const void *, unsigned long)'
./include/linux/string.h:159:12: error: incompatible redeclaration of library function 'bcmp' [-Werror,-Wincompatible-library-redeclaration]
extern int bcmp(const void *,const void *,__kernel_size_t);
           ^
./include/linux/string.h:159:12: note: 'bcmp' is a builtin with type 'int (const void *, const void *, unsigned long)'
15 errors generated.

[nathanchance]

I cannot reproduce this or #1857 with LLVM at llvm/llvm-project@99a1aee + D151741 and Linux 6.3.5:

$ curl -LSs https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.3.5.tar.xz | tar -xJf -

$ make -C linux-6.3.5 -skj"$(nproc)" ARCH=arm LLVM=1 O=build mrproper allyesconfig all
...

$ echo $status
0

[nickdesaulniers]

Strange, https://reviews.llvm.org/D151741 does indeed prevent these further warnings.