What is gxx personality v0 for

Question

This is a second-hand question from an OS development site  but it made me curious since I couldn t find a decent explanation anywhere   When compiling and linking a free-standing C   program using gcc  sometimes a linker error like this occurs   out kernel o   eh frame 0x11   undefined reference to    gxx personality v0    This is apparently because this symbol is defined in libstdc    which is missing in a free-standing environment  Fixing the problem simply requires defining this symbol somewhere   void    gxx personality v0    Which is nice  but I don t like things that just magically work    So the question is  what is the purpose of this symbol

User · Answer

I had this error once and I found out the origin:

I was using a gcc compiler and my file was called CLIENT.C despite I was doing a C program and not a C++ program.

gcc recognizes the .C extension as C++ program and .c extension as C program (be careful to the small c and big C).

So I renamed my file CLIENT.c program and it worked.

User · Answer

The answers above are correct  it is used in exception handling   The manual for GCC version 6 has more information  which is no longer present in the version 7 manual    The error can arise when linking an external function that - unknown to GCC - throws Java exceptions

User · Answer

A quick grep of the libstd   code base revealed the following two usages of   gx personality v0   In libsupc   unwind-cxx h     GNU C   personality routine  Version 0                                        extern  C   Unwind Reason Code   gxx personality v0       int   Unwind Action   Unwind Exception Class        struct  Unwind Exception    struct  Unwind Context       In libsupc   eh personality cc   define PERSONALITY FUNCTION      gxx personality v0 extern  C   Unwind Reason Code PERSONALITY FUNCTION  int version                         Unwind Action actions                         Unwind Exception Class exception class                        struct  Unwind Exception  ue header                        struct  Unwind Context  context             code to handle exceptions and stuff          Note  it s actually a little more complicated than that  there s some conditional compilation that can change some details    So  as long as your code isn t actually using exception handling  defining the symbol as void  won t affect anything  but as soon as it does  you re going to crash -   gxx personality v0 is a function  not some global object  so trying to call the function is going to jump to address 0 and cause a segfault

User · Answer

A quick grep of the libstd   code base revealed the following two usages of   gx personality v0   In libsupc   unwind-cxx h     GNU C   personality routine  Version 0                                        extern  C   Unwind Reason Code   gxx personality v0       int   Unwind Action   Unwind Exception Class        struct  Unwind Exception    struct  Unwind Context       In libsupc   eh personality cc   define PERSONALITY FUNCTION      gxx personality v0 extern  C   Unwind Reason Code PERSONALITY FUNCTION  int version                         Unwind Action actions                         Unwind Exception Class exception class                        struct  Unwind Exception  ue header                        struct  Unwind Context  context             code to handle exceptions and stuff          Note  it s actually a little more complicated than that  there s some conditional compilation that can change some details    So  as long as your code isn t actually using exception handling  defining the symbol as void  won t affect anything  but as soon as it does  you re going to crash -   gxx personality v0 is a function  not some global object  so trying to call the function is going to jump to address 0 and cause a segfault

User · Answer

It s part of the exception handling  The gcc EH mechanism allows to mix various EH models  and a personality routine is invoked to determine if an exception match  what finalization to invoke  etc  This specific personality routine is for C   exception handling  as opposed to  say  gcj Java exception handling

User · Answer

Exception handling is included in free standing implementations    The reason of this is that you possibly use gcc to compile your code  If you compile with the option -    you will notice it is missing the linker-option -lstdc   when it invokes the linker process   Compiling with g   will include that library  and thus the symbols defined in it

User · Answer

It s part of the exception handling  The gcc EH mechanism allows to mix various EH models  and a personality routine is invoked to determine if an exception match  what finalization to invoke  etc  This specific personality routine is for C   exception handling  as opposed to  say  gcj Java exception handling

User · Answer

It is used in the stack unwiding tables  which you can see for instance in the assembly output of my answer to another question  As mentioned on that answer  its use is defined by the Itanium C   ABI  where it is called the Personality Routine   The reason it  works  by defining it as a global NULL void pointer is probably because nothing is throwing an exception  When something tries to throw an exception  then you will see it misbehave   Of course  if nothing is using exceptions  you can disable them with -fno-exceptions  and if nothing is using RTTI  you can also add -fno-rtti   If you are using them  you have to  as other answers already noted  link with g   instead of gcc  which will add -lstdc   for you

User · Answer

It is used in the stack unwiding tables  which you can see for instance in the assembly output of my answer to another question  As mentioned on that answer  its use is defined by the Itanium C   ABI  where it is called the Personality Routine   The reason it  works  by defining it as a global NULL void pointer is probably because nothing is throwing an exception  When something tries to throw an exception  then you will see it misbehave   Of course  if nothing is using exceptions  you can disable them with -fno-exceptions  and if nothing is using RTTI  you can also add -fno-rtti   If you are using them  you have to  as other answers already noted  link with g   instead of gcc  which will add -lstdc   for you

User · Answer

It is used in the stack unwiding tables  which you can see for instance in the assembly output of my answer to another question  As mentioned on that answer  its use is defined by the Itanium C   ABI  where it is called the Personality Routine   The reason it  works  by defining it as a global NULL void pointer is probably because nothing is throwing an exception  When something tries to throw an exception  then you will see it misbehave   Of course  if nothing is using exceptions  you can disable them with -fno-exceptions  and if nothing is using RTTI  you can also add -fno-rtti   If you are using them  you have to  as other answers already noted  link with g   instead of gcc  which will add -lstdc   for you

User · Answer

Exception handling is included in free standing implementations    The reason of this is that you possibly use gcc to compile your code  If you compile with the option -    you will notice it is missing the linker-option -lstdc   when it invokes the linker process   Compiling with g   will include that library  and thus the symbols defined in it

User · Answer

It is used in the stack unwiding tables  which you can see for instance in the assembly output of my answer to another question  As mentioned on that answer  its use is defined by the Itanium C   ABI  where it is called the Personality Routine   The reason it  works  by defining it as a global NULL void pointer is probably because nothing is throwing an exception  When something tries to throw an exception  then you will see it misbehave   Of course  if nothing is using exceptions  you can disable them with -fno-exceptions  and if nothing is using RTTI  you can also add -fno-rtti   If you are using them  you have to  as other answers already noted  link with g   instead of gcc  which will add -lstdc   for you

User · Answer

The answers above are correct  it is used in exception handling   The manual for GCC version 6 has more information  which is no longer present in the version 7 manual    The error can arise when linking an external function that - unknown to GCC - throws Java exceptions

User · Answer

Exception handling is included in free standing implementations    The reason of this is that you possibly use gcc to compile your code  If you compile with the option -    you will notice it is missing the linker-option -lstdc   when it invokes the linker process   Compiling with g   will include that library  and thus the symbols defined in it

User · Answer

A quick grep of the libstd   code base revealed the following two usages of   gx personality v0   In libsupc   unwind-cxx h     GNU C   personality routine  Version 0                                        extern  C   Unwind Reason Code   gxx personality v0       int   Unwind Action   Unwind Exception Class        struct  Unwind Exception    struct  Unwind Context       In libsupc   eh personality cc   define PERSONALITY FUNCTION      gxx personality v0 extern  C   Unwind Reason Code PERSONALITY FUNCTION  int version                         Unwind Action actions                         Unwind Exception Class exception class                        struct  Unwind Exception  ue header                        struct  Unwind Context  context             code to handle exceptions and stuff          Note  it s actually a little more complicated than that  there s some conditional compilation that can change some details    So  as long as your code isn t actually using exception handling  defining the symbol as void  won t affect anything  but as soon as it does  you re going to crash -   gxx personality v0 is a function  not some global object  so trying to call the function is going to jump to address 0 and cause a segfault

User · Answer

Exception handling is included in free standing implementations    The reason of this is that you possibly use gcc to compile your code  If you compile with the option -    you will notice it is missing the linker-option -lstdc   when it invokes the linker process   Compiling with g   will include that library  and thus the symbols defined in it

User · Answer

I had this error once and I found out the origin:

I was using a gcc compiler and my file was called CLIENT.C despite I was doing a C program and not a C++ program.

gcc recognizes the .C extension as C++ program and .c extension as C program (be careful to the small c and big C).

So I renamed my file CLIENT.c program and it worked.

User · Answer

It s part of the exception handling  The gcc EH mechanism allows to mix various EH models  and a personality routine is invoked to determine if an exception match  what finalization to invoke  etc  This specific personality routine is for C   exception handling  as opposed to  say  gcj Java exception handling

User · Answer

A quick grep of the libstd   code base revealed the following two usages of   gx personality v0   In libsupc   unwind-cxx h     GNU C   personality routine  Version 0                                        extern  C   Unwind Reason Code   gxx personality v0       int   Unwind Action   Unwind Exception Class        struct  Unwind Exception    struct  Unwind Context       In libsupc   eh personality cc   define PERSONALITY FUNCTION      gxx personality v0 extern  C   Unwind Reason Code PERSONALITY FUNCTION  int version                         Unwind Action actions                         Unwind Exception Class exception class                        struct  Unwind Exception  ue header                        struct  Unwind Context  context             code to handle exceptions and stuff          Note  it s actually a little more complicated than that  there s some conditional compilation that can change some details    So  as long as your code isn t actually using exception handling  defining the symbol as void  won t affect anything  but as soon as it does  you re going to crash -   gxx personality v0 is a function  not some global object  so trying to call the function is going to jump to address 0 and cause a segfault

User · Answer

It s part of the exception handling  The gcc EH mechanism allows to mix various EH models  and a personality routine is invoked to determine if an exception match  what finalization to invoke  etc  This specific personality routine is for C   exception handling  as opposed to  say  gcj Java exception handling

[c++] What is __gxx_personality_v0 for?

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