Md unwind support h 65 47 error dereferencing pointer to incomplete type struct ucontext

gcc-6.3.0 build error on Fedora 27 #5758

I was running a test build for #5735 and it failed at the first hurdle with this error for gcc-6.3.0 :

make[2]: *** [../../../libgcc/shared-object.mk:14: unwind-dw2.o] Error 1 make[2]: *** Waiting for unfinished jobs. make[2]: Leaving directory ‘/dev/shm/GCCcore/6.3.0/dummy-/gcc-6.3.0/stage1_obj/x86_64-pc-linux-gnu/libgcc’ make[1]: *** [Makefile:14075: all-target-libgcc] Error 2 make[1]: Leaving directory ‘/dev/shm/GCCcore/6.3.0/dummy-/gcc-6.3.0/stage1_obj’ make: *** [Makefile:888: all] Error 2″>

The text was updated successfully, but these errors were encountered:

same on ubuntu 17.10

I run into the same problem when building the foss-2018a toolchain when getting to GCC-6.4.0. I think this is related to this issue: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81712

This was fixed for GCC-7XX and also backported to the 5 and 6 series but only comes with updated versions 5.5 and 6.5. I would suggest to at least include 6.5 in the next foos-2018b toolchain revision.

As a workaround to compile gcc code with glibc 2.26+ one can change struct ucontext to ucontext_t in the gcc source as suggested here: suaefar/ryzen-test#6 , but I haven’t tried it, yet.

We fixed this for GCCcore 6.4.0 in #6432 (+ #6495)

foss/2018b includes GCC(core) 7.3.0, as far as I know there’s no problem there.

It’s likely that the patch in #6432 also works for GCC 6.3.0, can someone try this?

Ah ok I see. Mmmm. but why is my build failing? Also when I check the supposed to be patched file libgcc/config/aarch64/linux-unwind.h in the build directory, it is not patched. Still using struct ucontext uc What am I missing here? I’m on Ubuntu 18.04 btw.

@seb45tian #6432 is not included yet in the latest EasyBuild release (3.6.1), but will be in the next one (3.6.2), which should be available shortly (in a couple of hours even, if all goes well. ).

Ah thanks for the hint, and also the patch. Think this one can be closed then.
Cheers

Well, the issue is still there for GCC 6.3.0, so I’ll leave it up to @verdurin whether we can close this or not. Should we make the effort of also applying the patch in the GCCcore 6.3.0 easyconfig?

@verdurin Is it worth the trouble to also try to fix this for GCCcore 6.3.0?

Источник

Include a successful output file about ryzen-test HOT 3 OPEN

Yes, the issue is known. Remember that this script does not calculate anything deterministic. It is likely to trigger a hardware bug under certain conditions (Ubuntu 17.04!). I cant change it without risking that it looses this property.

Yes, I can add the output of a sucessful run.

0x647262 commented on January 16, 2023

Adding to this, a buildloop can fail because of issues unrelated to segfaulting.

make[3]: *** [/mnt/ramdisk/workdir/gcc-7.1.0/libgcc/shared-object.mk:14: unwind-dw2.o] Error 1 make[3]: *** Waiting for unfinished jobs. make[3]: Leaving directory ‘/mnt/ramdisk/workdir/buildloop.d/loop-3/x86_64-pc-linux-gnu/libgcc’ make[2]: *** [Makefile:21950: all-stage1-target-libgcc] Error 2 make[2]: Leaving directory ‘/mnt/ramdisk/workdir/buildloop.d/loop-3’ make[1]: *** [Makefile:27079: stage1-bubble] Error 2 make[1]: Leaving directory ‘/mnt/ramdisk/workdir/buildloop.d/loop-3’ make: *** [Makefile:942: all] Error 2″>

I’ll open a PR for this when I have some time. Nevermind, I see this repository is frozen.

0x647262 commented on January 16, 2023

• zram mount error HOT 6
• the script couldn’t run on arch linux HOT 3
• Add Archlinux support HOT 7
• Compilation fails with current Artful toolchain HOT 11
• Correct testing procedure HOT 18
• Will this bug can be fixed by gcc update or kernel patch？ HOT 9
• [PSA] Default settings on motherboards set RAM to low frequency & low voltage on VDDCR_SOC & other RAM settings may cause a false postive segfault! HOT 5
• Is this still valid? HOT 50
• Ubuntu LTS version? HOT 6
• Is my CPU buggy? HOT 7
• Ryzen 2700x first fail report or expected output? HOT 2
• Does «build failed» mean anything? HOT 3
• Memory runs out before tests finishes HOT 2
• 2010-03-15 Running on Ubuntu 18.04, Linux Mint 19 Tara, gcc sources 8.3.0
• Error on Ryzen 7 2700x
• this script makes my ryzen 3500u lock up i thought the bug was fixed with ryzen 2000 series
• Seems to be stuck at loop-11 HOT 2
• on archlinux the gcc 7.1 build fails HOT 5
• Could we get a script for cleaning up afterwards? (or at least instructions) HOT 10

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on archlinux the gcc 7.1 build fails about ryzen-test HOT 5 CLOSED

As a workaround to compile gcc code with glibc 2.26+ you can change struct ucontext to ucontext_t in the gcc source.

BuzzBumbleBee commented on January 16, 2023

@ChristophHaag see my PR, seems to work fine on arch (as of yesterday) for me

suaefar commented on January 16, 2023

Sorry, but I had to remove the support for Arch. I suppose Arch users know what to do to get the script running, or how to reproduce the buggy behaviour for that matter. The problem with Arch is, that I can’t rely on a standard version of, e.g., gcc. The reference implementation will be based on Ubuntu.

ttbek commented on January 16, 2023

I updated my Arch yesterday and got this error running the script this morning, if it is fixed upstream it may not have filtered down into Arch yet. Before my update it was building on Arch quite happily. I get that you only want to support a single OS, but it will be good for people to know they may encounter this issue, I will update the AMD forum thread. I’m not quite clear on the referenced link, they updated gcc or glib? Looks like gcc to me, so they decided glib is behaving correctly. I did switch to gcc-multilib (needed to make some 32 bit static binaries) though, maybe the change didn’t reach the multilib version yet.
I wouldn’t assume Arch users are necessarily that much more advanced. I’m actually running Arch because when I was installing my OS Ubuntu had significant problems running on the Gigabyte X370 K7 board. and turns out Gigabyte doesn’t give a hoot.

Oxalin commented on January 16, 2023

Not related to rolling release distributions. Problem comes with glib 2.26 under gcc 7.1.0 known bug and fixed, but not backported), which is fixed under gcc 7.2: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81712

Updating the script to download gcc 7.2.0 (.tar.xz please) should fix the problem.

• zram mount error HOT 6
• the script couldn’t run on arch linux HOT 3
• Add Archlinux support HOT 7
• Compilation fails with current Artful toolchain HOT 11
• Correct testing procedure HOT 18
• Will this bug can be fixed by gcc update or kernel patch？ HOT 9
• Include a successful output file HOT 3
• [PSA] Default settings on motherboards set RAM to low frequency & low voltage on VDDCR_SOC & other RAM settings may cause a false postive segfault! HOT 5
• Is this still valid? HOT 50
• Ubuntu LTS version? HOT 6
• Is my CPU buggy? HOT 7
• Ryzen 2700x first fail report or expected output? HOT 2
• Does «build failed» mean anything? HOT 3
• Memory runs out before tests finishes HOT 2
• 2010-03-15 Running on Ubuntu 18.04, Linux Mint 19 Tara, gcc sources 8.3.0
• Error on Ryzen 7 2700x
• this script makes my ryzen 3500u lock up i thought the bug was fixed with ryzen 2000 series
• Seems to be stuck at loop-11 HOT 2
• Could we get a script for cleaning up afterwards? (or at least instructions) HOT 10

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Include a successful output file about ryzen-test HOT 3 OPEN

Yes, the issue is known. Remember that this script does not calculate anything deterministic. It is likely to trigger a hardware bug under certain conditions (Ubuntu 17.04!). I cant change it without risking that it looses this property.

Yes, I can add the output of a sucessful run.

0x647262 commented on January 16, 2023

Adding to this, a buildloop can fail because of issues unrelated to segfaulting.

make[3]: *** [/mnt/ramdisk/workdir/gcc-7.1.0/libgcc/shared-object.mk:14: unwind-dw2.o] Error 1 make[3]: *** Waiting for unfinished jobs. make[3]: Leaving directory ‘/mnt/ramdisk/workdir/buildloop.d/loop-3/x86_64-pc-linux-gnu/libgcc’ make[2]: *** [Makefile:21950: all-stage1-target-libgcc] Error 2 make[2]: Leaving directory ‘/mnt/ramdisk/workdir/buildloop.d/loop-3’ make[1]: *** [Makefile:27079: stage1-bubble] Error 2 make[1]: Leaving directory ‘/mnt/ramdisk/workdir/buildloop.d/loop-3’ make: *** [Makefile:942: all] Error 2″>

I’ll open a PR for this when I have some time. Nevermind, I see this repository is frozen.

0x647262 commented on January 16, 2023

• zram mount error HOT 6
• the script couldn’t run on arch linux HOT 3
• Add Archlinux support HOT 7
• Compilation fails with current Artful toolchain HOT 11
• Correct testing procedure HOT 18
• Will this bug can be fixed by gcc update or kernel patch？ HOT 9
• [PSA] Default settings on motherboards set RAM to low frequency & low voltage on VDDCR_SOC & other RAM settings may cause a false postive segfault! HOT 5
• Is this still valid? HOT 50
• Ubuntu LTS version? HOT 6
• Is my CPU buggy? HOT 7
• Ryzen 2700x first fail report or expected output? HOT 2
• Does «build failed» mean anything? HOT 3
• Memory runs out before tests finishes HOT 2
• 2010-03-15 Running on Ubuntu 18.04, Linux Mint 19 Tara, gcc sources 8.3.0
• Error on Ryzen 7 2700x
• this script makes my ryzen 3500u lock up i thought the bug was fixed with ryzen 2000 series
• Seems to be stuck at loop-11 HOT 2
• on archlinux the gcc 7.1 build fails HOT 5
• Could we get a script for cleaning up afterwards? (or at least instructions) HOT 10

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dereferencing pointer to incomplete type

Hello, I am making an application that implements doubly linked lists (each node has a pointer to the previous node and the next node), and I am am having trouble with the functions that service the list. I am getting a compiler error «dereferencing pointer to incomplete type», and I am unsure of how to proceed.

Here is the relevant code

I will get a lot of the same error on different statements in the add_front function. I am not sure why this happens either. Is there something fundamental about pointers/structs that I am not getting? Thanks in advance.

Last edited by kataya; 04-16-2008 at 01:29 AM .

You are doing wrong because you cannot use a name that technically hasn’t been defined yet. Instead, use the actual structure name:

Also note that since you are using typedef, you should not be typing «struct» before it, because lnode is a typedef for «struct _lnode.» That means «struct lnode» becomes «struct struct _lnode,» which you can see is wrong.

You mean it’s included as a crutch to help ancient programmers limp along without them having to relearn too much.

Outside of your DOS world, your header file is meaningless.

Ah nice, it compiles now. Thanks much for the fix and more so for the explanation.

Источник

1. Causes of the dereferencing pointer to incomplete type Error in C
2. Incomplete Types in C
3. Referencing and Dereferencing a Pointer in C
4. Solve the dereferencing pointer to incomplete type Error in C
5. Conclusion

It is known that a pointer is used to store the address of values stored inside a variable. This pointer variable can be referenced to a variable to get its address or dereferenced to access its value.

But when this pointer needs to be seen or edited, it must be dereferenced. When this dereferencing is done through a declared but not defined type, it throws the error dereferencing pointer to incomplete type.

Causes of the dereferencing pointer to incomplete type Error in C

This error is caused when the compiler comes across a pointer being dereferenced to a struct. When the compiler moves towards the struct, it finds it incomplete, i.e., not defined properly.

The compiler throws different errors when an undefined struct is called to deference a pointer. The type of error encountered depends on the compiler used.

the dereferencing pointer to incomplete type Error in GCC Compiler

For example, an undefined struct looks like this:

struct circle {
	int length;
};
int main() {
    struct round *x = 0;
    *x;
}

In the above C program, it can be observed that a struct circle is constructed, but the struct called inside the main function has the name round.

Inside the main function, an object pointer *x is created from the struct round. Lastly, the pointer object is called.

Here, an incomplete struct is used as if it is a complete struct, which causes the compiler to throw the error.

1035906452/source.c: In function 'main':
1035906452/source.c:6:5: error: dereferencing pointer to incomplete type 'struct round'
     *x;
     ^~

It can be observed that the compiler throws the error dereferencing pointer to incomplete type.

Normally, C will find the name of the struct which was put in; if the original struct is not found, this would usually appear. It will also appear if you point a pointer pointed into that pointer.

This error typically appears if the name of your struct is different from the initialization of your struct in the code.

A struct can also throw errors when given an alias that the compiler cannot read, but that does not happen with every compiler.

the dereferencing pointer to incomplete type Error in Clang Compiler

This is encountered when the same code is run through a Clang compiler.

1790191360/source.c:6:5: error: incomplete type 'struct round' where a complete type is required
    *x;
    ^
1790191360/source.c:5:12: note: forward declaration of 'struct round'
    struct round *x = 0;
           ^
1790191360/source.c:6:5: warning: expression result unused [-Wunused-value]
    *x;
    ^~
1 warning and 1 error generated.

Here, the compiler calls out the incomplete struct but leaves the dereferenced pointer as a warning instead of an error.

Understanding why the error dereferencing pointer to incomplete type happens requires knowing two concepts.

1. What are incomplete types?
2. What does dereferencing a pointer mean?

Incomplete Types in C

A type declared but not specified is incomplete (in the case of struct types).

Typos in type names, which prevent the compiler from matching one name to the other, are a common cause of incomplete type errors in the C language (like in matching the declaration to the definition).

It is a misconception to think that an incomplete type is a missing type. Incomplete types can occur outside struct too.

Three scenarios cause incomplete type:

1. A struct type with no members.
2. A union type with no members.
3. An array that is declared but no element is inserted.

Create an Incomplete Type and Define It

A struct or a type that is similar needs to be specified with the information lacking to complete an incomplete type.

The creation and completion of the incomplete types are demonstrated in the examples below.

Declare a structure type but omit the members to produce an incomplete structure type. The x pointer in this illustration points to an incomplete structure type named library.

Declare the same structure type later in the same scope with its members provided to complete an incomplete structure type.

struct library
{
    int book_id;
    char book_name[50];
}

To create an array of incomplete types, declare an array type without specifying its repetition count. For instance:

char book_name[];  /* book_name has incomplete type */

Declare the same name later in the same scope with its repetition count set to finish an incomplete array type.

char book_name[25]; /* book_name now has complete type */

Once we have understood how incomplete types are completed, we can go to the second part of solving the dereferencing pointer to incomplete type error.

Referencing and Dereferencing a Pointer in C

The function of a pointer is to store the address of a value, which means it stores a reference to something. The object to which a pointer point is called a pointee.

Referencing a Pointer in C

There are two distinct stages involved in allocating a pointer and a pointee to which it will point. The pointer/pointee structure can be thought of as having two levels of operation.

Everything needs to be set up on both levels for it to work. The most frequent mistake is to focus on writing code that manipulates the pointer level while neglecting to set up the pointee level.

Pointer operations that do not contact the pointees are sometimes referred to as “shallow” operations, while those that do are referred to as “deep” operations.

Consider the following code:

A pointer ptr_a is created inside the main function. This pointer is created but cannot store something unless a pointee or a memory chunk is allocated.

The allocation of memory is done by malloc, and the size given is equivalent to data type int.

void main() {
    int*    ptr_a;  // Allocate the pointer

    ptr_a = malloc(sizeof(int));    // Allocate an int pointee, and set ptr_a to point to it
}

C++ code:

int main() {
    int*    ptr_a;  // Allocate the pointer ptr_a

    ptr_a = new int;    // Allocate an int pointee, and set ptr_a to point to it
}

Dereferencing a Pointer in C

Dereference operations begin at the pointer and follow up to the pointee. The objective could be to examine or modify the pointee state.

A pointer can only be dereferenced if it has a pointee; the pointee must also be allocated before the pointer can be made to point at it. Forgetting to set up the pointee is the most frequent mistake in pointer programs.

Failure in code to successfully dereference a pointer is the most common runtime crash. The runtime system in Java flags the issue of improper dereferences with minor warnings.

In compiled languages like C and C++, a bad dereference can cause a crash or cause spontaneous memory corruption. This makes it challenging to find pointer issues in compiled languages.

C code:

Once the memory is allocated and pointed towards pointer ptr_a, a value is stored inside it by dereferencing it.

void main()  {
	int*    ptr_a;

	ptr_a = malloc(sizeof(int));    // Allocate an int pointee, and set ptr_a to point to it

	*ptr_a = 42;    // Dereference ptr_a to store 42 in its pointee
}

C++ code:

int main() {
    int*    ptr_a;  // Allocate the pointers

    ptr_a = new int;    // Allocate an int pointee, and set ptr_a to point to it

    *ptr_a = 42;    // Dereference ptr_a to store 42 in its pointee
}

Shared Pointers in C

When two pointers are assigned to the same pointee, they will both point there. As a result, y points to the same pointee as x when y = x.

The pointees are unaffected by pointer assignment.

It only modifies one pointer to share the same reference as another. After the pointer assignment, the two pointers are considered “sharing” the pointee.

C code:

void main() {
    int*    ptr_a;
    int*    ptr_b;

    ptr_a = malloc(sizeof(int));

    *ptr_a = 42;

    *ptr_b = 13;    // CRASH -- ptr_b does not have a pointee yet

    ptr_b = ptr_a;      // Pointer assignment sets ptr_b to point to ptr_a's pointee

    *ptr_b = 13;    // Dereference ptr_b to store 13 in its (shared) pointee
}

We have understood the two concepts behind solving the dereferencing pointer to incomplete type error. We will now look at the codes that encounter the error and how to solve the issue.

Solve the dereferencing pointer to incomplete type Error in C

The below program has a struct rectangle with an integer member length. The name of the struct is deliberately made different than the one inside the main function to create an incomplete type.

Inside the main function, the pointer *a is created and allocated memory of the struct rectangle size, and then it is pointed towards it.

Then the pointer is used to dereference the struct member length to store a value inside it. As the struct is of incomplete type, it must throw a dereferencing pointer to incomplete type error.

#include<stdio.h>
#include<stdlib.h>

struct rectangle{
	int length;
};

int main() {
	struct square *a;
	a = (struct rectngle*)malloc(sizeof(struct rectngle));
	a->length = 33;
	printf("%d",*a);
}

Output:

1647679200/source.c: In function 'main':
1647679200/source.c:10:38: error: invalid application of 'sizeof' to incomplete type 'struct rectngle'
  a = (struct rectngle*)malloc(sizeof(struct rectngle));
                                      ^~~~~~
1647679200/source.c:11:3: error: dereferencing pointer to incomplete type 'struct square'
  a->length = 33;
   ^~

The incomplete type must be completed to resolve this issue, which in this case is the struct rectngle.

These changes must be made to complete an incomplete struct and dereference its members through a pointer inside the main function.

#include<stdio.h>
#include<stdlib.h>

struct rectangle{			// a struct rectngle is created
	int length;
};

int main() {
	struct rectangle *a;		//name of struct inside main() is same as above struct

	a = (struct rectangle*)malloc(sizeof(struct rectangle)); /*pointer allocated memory and
													  pointer to pointer 'a'.   */

    a->length = 33;									   //pointer deferenced.

	printf("%d",*a);								  //value of pointer dereferenced
}

Output:

Conclusion

This article sheds light on the error that arises due to dereferencing pointer to incomplete type. After going through this article, the reader can easily reference and deference pointers and complete incomplete types.