[PATCH] Change function signature passed to clone

[PATCH] Change function signature passed to clone

[Yao Qi]

I see the following compile error with an old bfin-uclinux gcc to
build GDBserver,

 cc1: warnings being treated as errors
 gdb/gdbserver/../nat/linux-ptrace.c: In function 'linux_fork_to_function':
 gdb/gdbserver/../nat/linux-ptrace.c:283: error: passing argument 1 of 'clone' from incompatible pointer type

in glibc, clone's prototype is like this, and in uClibc, it is the same,

       int clone(int (*fn)(void *), void *child_stack,
                 int flags, void *arg, ...
                 /* pid_t *ptid, struct user_desc *tls, pid_t *ctid */ );

so this patch changes function signature from 'void (*function) (gdb_byte *)'
to 'int (*function) (void *)'.

Note that I find Pedro advised to change argument type from 'void *'
to 'gdb_byte *' during the patch review
https://sourceware.org/ml/gdb-patches/2013-08/msg00611.html  however,
I think fix compile error can justify the change back to 'void *'.

gdb:

2016-01-08  Yao Qi  <yao.qi@linaro.org>

	* nat/linux-ptrace.c (linux_fork_to_function): Change type
	of argument 'function'.
	(linux_grandchild_function): Change return type to 'int'.
	Change child_stack's type to 'void *'.
	(linux_child_function): Likewise.
---
 gdb/nat/linux-ptrace.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
index f25abcf..31757ee 100644
--- a/gdb/nat/linux-ptrace.c
+++ b/gdb/nat/linux-ptrace.c
@@ -261,7 +261,7 @@ linux_ptrace_test_ret_to_nx (void)
    FUNCTION).  For MMU targets, CHILD_STACK is ignored.  */
 
 static int
-linux_fork_to_function (gdb_byte *child_stack, void (*function) (gdb_byte *))
+linux_fork_to_function (gdb_byte *child_stack, int (*function) (void *))
 {
   int child_pid;
 
@@ -298,8 +298,8 @@ linux_fork_to_function (gdb_byte *child_stack, void (*function) (gdb_byte *))
 /* A helper function for linux_check_ptrace_features, called after
    the child forks a grandchild.  */
 
-static void
-linux_grandchild_function (gdb_byte *child_stack)
+static int
+linux_grandchild_function (void *child_stack)
 {
   /* Free any allocated stack.  */
   xfree (child_stack);
@@ -313,8 +313,8 @@ linux_grandchild_function (gdb_byte *child_stack)
    the parent process forks a child.  The child allows itself to
    be traced by its parent.  */
 
-static void
-linux_child_function (gdb_byte *child_stack)
+static int
+linux_child_function (void *child_stack)
 {
   ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
   kill (getpid (), SIGSTOP);
-- 
1.9.1

Re: [PATCH] Change function signature passed to clone

[Pedro Alves]

On 01/08/2016 02:45 PM, Yao Qi wrote:
> I see the following compile error with an old bfin-uclinux gcc to
> build GDBserver,
> 
>  cc1: warnings being treated as errors
>  gdb/gdbserver/../nat/linux-ptrace.c: In function 'linux_fork_to_function':
>  gdb/gdbserver/../nat/linux-ptrace.c:283: error: passing argument 1 of 'clone' from incompatible pointer type
> 
> in glibc, clone's prototype is like this, and in uClibc, it is the same,
> 
>        int clone(int (*fn)(void *), void *child_stack,
>                  int flags, void *arg, ...
>                  /* pid_t *ptid, struct user_desc *tls, pid_t *ctid */ );
> 
> so this patch changes function signature from 'void (*function) (gdb_byte *)'
> to 'int (*function) (void *)'.
> 
> Note that I find Pedro advised to change argument type from 'void *'
> to 'gdb_byte *' during the patch review
> https://sourceware.org/ml/gdb-patches/2013-08/msg00611.html  however,
> I think fix compile error can justify the change back to 'void *'.

Agreed, LGTM.

Thanks,
Pedro Alves

Re: [PATCH] Change function signature passed to clone

[Yao Qi]

Pedro Alves <palves@redhat.com> writes:

>> Note that I find Pedro advised to change argument type from 'void *'
>> to 'gdb_byte *' during the patch review
>> https://sourceware.org/ml/gdb-patches/2013-08/msg00611.html  however,
>> I think fix compile error can justify the change back to 'void *'.
>
> Agreed, LGTM.

Thanks, patch is pushed in.

-- 
Yao (齐尧)

Re: [PATCH] Change function signature passed to clone

[Yao Qi]

Yao Qi <qiyaoltc@gmail.com> writes:

> diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
> index f25abcf..31757ee 100644
> --- a/gdb/nat/linux-ptrace.c
> +++ b/gdb/nat/linux-ptrace.c
> @@ -261,7 +261,7 @@ linux_ptrace_test_ret_to_nx (void)
>     FUNCTION).  For MMU targets, CHILD_STACK is ignored.  */
>  
>  static int
> -linux_fork_to_function (gdb_byte *child_stack, void (*function) (gdb_byte *))
> +linux_fork_to_function (gdb_byte *child_stack, int (*function) (void *))
>  {
>    int child_pid;
>  
> @@ -298,8 +298,8 @@ linux_fork_to_function (gdb_byte *child_stack, void (*function) (gdb_byte *))
>  /* A helper function for linux_check_ptrace_features, called after
>     the child forks a grandchild.  */
>  
> -static void
> -linux_grandchild_function (gdb_byte *child_stack)
> +static int
> +linux_grandchild_function (void *child_stack)
>  {
>    /* Free any allocated stack.  */
>    xfree (child_stack);
> @@ -313,8 +313,8 @@ linux_grandchild_function (gdb_byte *child_stack)
>     the parent process forks a child.  The child allows itself to
>     be traced by its parent.  */
>  
> -static void
> -linux_child_function (gdb_byte *child_stack)
> +static int
> +linux_child_function (void *child_stack)
>  {
>    ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
>    kill (getpid (), SIGSTOP);

This patch causes a C++ build error.  Patch below fixes it.

-- 
Yao (齐尧)

Subject: [PATCH] Fix invalid conversion from void * to gdb_byte *

This patch fixes the following GDB build error in C++ mode.

gdb/nat/linux-ptrace.c: In function 'int linux_child_function(void*)':
gdb/nat/linux-ptrace.c:323:65: error: invalid conversion from 'void*' to 'gdb_byte* {aka unsigned char*}' [-fpermissive]
   linux_fork_to_function (child_stack, linux_grandchild_function);
                                                                 ^

gdb:

2016-01-12  Yao Qi  <yao.qi@linaro.org>

	* nat/linux-ptrace.c (linux_child_function): Cast child_stack
	to gdb_byte * and pass to linux_fork_to_function.

diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
index 31757ee..0eaf9a3 100644
--- a/gdb/nat/linux-ptrace.c
+++ b/gdb/nat/linux-ptrace.c
@@ -320,7 +320,7 @@ linux_child_function (void *child_stack)
   kill (getpid (), SIGSTOP);
 
   /* Fork a grandchild.  */
-  linux_fork_to_function (child_stack, linux_grandchild_function);
+  linux_fork_to_function ((gdb_byte *) child_stack, linux_grandchild_function);
 
   /* This code is only reacheable by the child (grandchild's parent)
      process.  */