From: Carlos Santos &lt;unixmania(a)gmail.com&gt; The return type of syscall() is long so __syscall_error, which is jumped to by syscall handlers to stash an error number into errno, must return long too otherwhise it returs 4294967295L instead of -1L. For example, syscall for x86_64 is defined in libc/sysdeps/linux/x86_64/syscall.S as syscall: movq %rdi, %rax /* Syscall number -> rax. */ movq %rsi, %rdi /* shift arg1 - arg5. */ movq %rdx, %rsi movq %rcx, %rdx movq %r8, %r10 movq %r9, %r8 movq 8(%rsp),%r9 /* arg6 is on the stack. */ syscall /* Do the system call. */ cmpq $-4095, %rax /* Check %rax for error. */ jae __syscall_error /* Branch forward if it failed. */ ret /* Return to caller. */ In libc/sysdeps/linux/x86_64/__syscall_error.c, __syscall_error is defined as int __syscall_error(void) attribute_hidden; int __syscall_error(void) { register int err_no __asm__ ("%rcx"); __asm__ ("mov %rax, %rcx\n\t" "neg %rcx"); __set_errno(err_no); return -1; } So __syscall_error returns -1 as a 32-bit int in a 64-bit register, %rax (0x00000000ffffffff, whose decimal value is decimal 4294967295) and a test like this always returns false: if (syscall(number, ...) == -1) foo(); Fix the error by making __syscall_error return a long, like syscall(). The problem can be circumvented by the caller by coercing the returned value to int before comparing it to -1: if ((int) syscall(number, ...) == -1) foo(); The same problem probably occurs on other 64-bit systems but so far only x86_64 was tested, so this change must be considered experimental. Signed-off-by: Carlos Santos &lt;unixmania(a)gmail.com&gt; --- libc/sysdeps/linux/aarch64/__syscall_error.c | 4 ++-- libc/sysdeps/linux/alpha/__syscall_error.c | 2 +- libc/sysdeps/linux/arc/__syscall_error.c | 2 +- libc/sysdeps/linux/arm/__syscall_error.c | 4 ++-- libc/sysdeps/linux/csky/__syscall_error.c | 2 +- libc/sysdeps/linux/csky/clone.c | 2 +- libc/sysdeps/linux/frv/sysdep.c | 2 +- libc/sysdeps/linux/hppa/__syscall_error.c | 4 ++-- libc/sysdeps/linux/i386/__syscall_error.c | 4 ++-- libc/sysdeps/linux/ia64/__syscall_error.c | 4 ++-- libc/sysdeps/linux/m68k/__syscall_error.c | 4 ++-- libc/sysdeps/linux/metag/__syscall_error.c | 4 ++-- libc/sysdeps/linux/microblaze/__syscall_error.c | 4 ++-- libc/sysdeps/linux/mips/__syscall_error.c | 4 ++-- libc/sysdeps/linux/nds32/__syscall_error.c | 4 ++-- libc/sysdeps/linux/nios2/__syscall_error.c | 4 ++-- libc/sysdeps/linux/or1k/__syscall_error.c | 4 ++-- libc/sysdeps/linux/powerpc/__syscall_error.c | 4 ++-- libc/sysdeps/linux/riscv64/__syscall_error.c | 4 ++-- libc/sysdeps/linux/sparc/__syscall_error.c | 4 ++-- libc/sysdeps/linux/sparc64/__syscall_error.c | 4 ++-- libc/sysdeps/linux/tile/__syscall_error.c | 2 +- libc/sysdeps/linux/x86_64/__syscall_error.c | 4 ++-- libc/sysdeps/linux/xtensa/__syscall_error.c | 4 ++-- libpthread/nptl/sysdeps/unix/sysv/linux/__syscall_error.c | 4 ++-- 25 files changed, 44 insertions(+), 44 deletions(-) diff --git a/libc/sysdeps/linux/aarch64/__syscall_error.c b/libc/sysdeps/linux/aarch64/__syscall_error.c index 2b642e816..c682aae49 100644 --- a/libc/sysdeps/linux/aarch64/__syscall_error.c +++ b/libc/sysdeps/linux/aarch64/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/alpha/__syscall_error.c b/libc/sysdeps/linux/alpha/__syscall_error.c index 7c081f3b5..c986e484d 100644 --- a/libc/sysdeps/linux/alpha/__syscall_error.c +++ b/libc/sysdeps/linux/alpha/__syscall_error.c @@ -8,7 +8,7 @@ /* This routine is jumped to by all the syscall handlers, to stash an error number into errno. */ -int attribute_hidden __syscall_error (void) +long attribute_hidden __syscall_error (void) { register int err_no __asm__("$0"); __set_errno (err_no); diff --git a/libc/sysdeps/linux/arc/__syscall_error.c b/libc/sysdeps/linux/arc/__syscall_error.c index 962d743e4..7f30485a8 100644 --- a/libc/sysdeps/linux/arc/__syscall_error.c +++ b/libc/sysdeps/linux/arc/__syscall_error.c @@ -8,7 +8,7 @@ #include <errno.h> #include <sys/syscall.h> -int __syscall_error(int err_no) +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/arm/__syscall_error.c b/libc/sysdeps/linux/arm/__syscall_error.c index 2b642e816..c682aae49 100644 --- a/libc/sysdeps/linux/arm/__syscall_error.c +++ b/libc/sysdeps/linux/arm/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/csky/__syscall_error.c b/libc/sysdeps/linux/csky/__syscall_error.c index cc1fb5977..c6a4a14eb 100644 --- a/libc/sysdeps/linux/csky/__syscall_error.c +++ b/libc/sysdeps/linux/csky/__syscall_error.c @@ -8,7 +8,7 @@ #include <errno.h> #include <features.h> -int __syscall_error(int err_no) +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/csky/clone.c b/libc/sysdeps/linux/csky/clone.c index 991cb8962..f0fcc257b 100644 --- a/libc/sysdeps/linux/csky/clone.c +++ b/libc/sysdeps/linux/csky/clone.c @@ -9,7 +9,7 @@ #include <sysdep.h> #include <unistd.h> -extern int __syscall_error(int err_no); +extern long __syscall_error(int err_no); extern int __csky_clone ( int flags, diff --git a/libc/sysdeps/linux/frv/sysdep.c b/libc/sysdeps/linux/frv/sysdep.c index bfae12100..28beb418f 100644 --- a/libc/sysdeps/linux/frv/sysdep.c +++ b/libc/sysdeps/linux/frv/sysdep.c @@ -19,7 +19,7 @@ /* This routine is jumped to by all the syscall handlers, to stash an error number into errno. */ -int __syscall_error (int err_no) +long __syscall_error (int err_no) { __set_errno (-err_no); return -1; diff --git a/libc/sysdeps/linux/hppa/__syscall_error.c b/libc/sysdeps/linux/hppa/__syscall_error.c index 5e109a83b..af26cf6ab 100644 --- a/libc/sysdeps/linux/hppa/__syscall_error.c +++ b/libc/sysdeps/linux/hppa/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(err_no); return -1; diff --git a/libc/sysdeps/linux/i386/__syscall_error.c b/libc/sysdeps/linux/i386/__syscall_error.c index 36946bc6d..102ebbedb 100644 --- a/libc/sysdeps/linux/i386/__syscall_error.c +++ b/libc/sysdeps/linux/i386/__syscall_error.c @@ -25,8 +25,8 @@ #include <errno.h> #include <features.h> -int __syscall_error(void) attribute_hidden; -int __syscall_error(void) +long __syscall_error(void) attribute_hidden; +long __syscall_error(void) { register int eax __asm__ ("%eax"); int _errno = -eax; diff --git a/libc/sysdeps/linux/ia64/__syscall_error.c b/libc/sysdeps/linux/ia64/__syscall_error.c index 0727b2b53..cc2b13450 100644 --- a/libc/sysdeps/linux/ia64/__syscall_error.c +++ b/libc/sysdeps/linux/ia64/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(void) attribute_hidden; -int __syscall_error(void) +long __syscall_error(void) attribute_hidden; +long __syscall_error(void) { register int err_no __asm__("%r8"); __set_errno(err_no); diff --git a/libc/sysdeps/linux/m68k/__syscall_error.c b/libc/sysdeps/linux/m68k/__syscall_error.c index a29f6ffd6..2d2677521 100644 --- a/libc/sysdeps/linux/m68k/__syscall_error.c +++ b/libc/sysdeps/linux/m68k/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(void) attribute_hidden; -int __syscall_error(void) +long __syscall_error(void) attribute_hidden; +long __syscall_error(void) { register int err_no __asm__("%d0"); __set_errno(-err_no); diff --git a/libc/sysdeps/linux/metag/__syscall_error.c b/libc/sysdeps/linux/metag/__syscall_error.c index f97cd0126..3e82abe0d 100644 --- a/libc/sysdeps/linux/metag/__syscall_error.c +++ b/libc/sysdeps/linux/metag/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/microblaze/__syscall_error.c b/libc/sysdeps/linux/microblaze/__syscall_error.c index 2b642e816..c682aae49 100644 --- a/libc/sysdeps/linux/microblaze/__syscall_error.c +++ b/libc/sysdeps/linux/microblaze/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/mips/__syscall_error.c b/libc/sysdeps/linux/mips/__syscall_error.c index 5e109a83b..af26cf6ab 100644 --- a/libc/sysdeps/linux/mips/__syscall_error.c +++ b/libc/sysdeps/linux/mips/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(err_no); return -1; diff --git a/libc/sysdeps/linux/nds32/__syscall_error.c b/libc/sysdeps/linux/nds32/__syscall_error.c index 2aa6903e2..c8e6044a7 100644 --- a/libc/sysdeps/linux/nds32/__syscall_error.c +++ b/libc/sysdeps/linux/nds32/__syscall_error.c @@ -8,8 +8,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(err_no); return -1; diff --git a/libc/sysdeps/linux/nios2/__syscall_error.c b/libc/sysdeps/linux/nios2/__syscall_error.c index 2b642e816..c682aae49 100644 --- a/libc/sysdeps/linux/nios2/__syscall_error.c +++ b/libc/sysdeps/linux/nios2/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/or1k/__syscall_error.c b/libc/sysdeps/linux/or1k/__syscall_error.c index 1b7e8a394..7d1e09d91 100644 --- a/libc/sysdeps/linux/or1k/__syscall_error.c +++ b/libc/sysdeps/linux/or1k/__syscall_error.c @@ -17,11 +17,11 @@ #include <errno.h> -int __syscall_error (int err_no); +long __syscall_error (int err_no); /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error (int err_no) +long __syscall_error (int err_no) { __set_errno (err_no); return -1; diff --git a/libc/sysdeps/linux/powerpc/__syscall_error.c b/libc/sysdeps/linux/powerpc/__syscall_error.c index 5e109a83b..af26cf6ab 100644 --- a/libc/sysdeps/linux/powerpc/__syscall_error.c +++ b/libc/sysdeps/linux/powerpc/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(err_no); return -1; diff --git a/libc/sysdeps/linux/riscv64/__syscall_error.c b/libc/sysdeps/linux/riscv64/__syscall_error.c index 2b642e816..c682aae49 100644 --- a/libc/sysdeps/linux/riscv64/__syscall_error.c +++ b/libc/sysdeps/linux/riscv64/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/sparc/__syscall_error.c b/libc/sysdeps/linux/sparc/__syscall_error.c index 5e109a83b..af26cf6ab 100644 --- a/libc/sysdeps/linux/sparc/__syscall_error.c +++ b/libc/sysdeps/linux/sparc/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(err_no); return -1; diff --git a/libc/sysdeps/linux/sparc64/__syscall_error.c b/libc/sysdeps/linux/sparc64/__syscall_error.c index 5e109a83b..af26cf6ab 100644 --- a/libc/sysdeps/linux/sparc64/__syscall_error.c +++ b/libc/sysdeps/linux/sparc64/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(err_no); return -1; diff --git a/libc/sysdeps/linux/tile/__syscall_error.c b/libc/sysdeps/linux/tile/__syscall_error.c index a91fdff3a..31cab3799 100644 --- a/libc/sysdeps/linux/tile/__syscall_error.c +++ b/libc/sysdeps/linux/tile/__syscall_error.c @@ -6,7 +6,7 @@ #include <errno.h> #include <features.h> -int __syscall_error(int err_no) +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libc/sysdeps/linux/x86_64/__syscall_error.c b/libc/sysdeps/linux/x86_64/__syscall_error.c index 448f50983..7f0f388c4 100644 --- a/libc/sysdeps/linux/x86_64/__syscall_error.c +++ b/libc/sysdeps/linux/x86_64/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(void) attribute_hidden; -int __syscall_error(void) +long __syscall_error(void) attribute_hidden; +long __syscall_error(void) { register int err_no __asm__ ("%rcx"); __asm__ ("mov %rax, %rcx\n\t" diff --git a/libc/sysdeps/linux/xtensa/__syscall_error.c b/libc/sysdeps/linux/xtensa/__syscall_error.c index 2b642e816..c682aae49 100644 --- a/libc/sysdeps/linux/xtensa/__syscall_error.c +++ b/libc/sysdeps/linux/xtensa/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(-err_no); return -1; diff --git a/libpthread/nptl/sysdeps/unix/sysv/linux/__syscall_error.c b/libpthread/nptl/sysdeps/unix/sysv/linux/__syscall_error.c index 5e109a83b..af26cf6ab 100644 --- a/libpthread/nptl/sysdeps/unix/sysv/linux/__syscall_error.c +++ b/libpthread/nptl/sysdeps/unix/sysv/linux/__syscall_error.c @@ -10,8 +10,8 @@ /* This routine is jumped to by all the syscall handlers, to stash * an error number into errno. */ -int __syscall_error(int err_no) attribute_hidden; -int __syscall_error(int err_no) +long __syscall_error(int err_no) attribute_hidden; +long __syscall_error(int err_no) { __set_errno(err_no); return -1; -- 2.18.1