Telling gcc diagnostics apart

Question

I have a problem interpreting gcc (4.8.2) warnings & errors. More precisely, it's difficult to tell where one problem ends and another one starts. I have console-only access to the build machine, so using an IDE is not an option.

I really need to be able to tell individual issues apart quickly. Is there a way to make GCC insert something between distinct diagnostic messages?

Here is an example output I am getting:

/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp: In member function ‘virtual bool xmodel::Core::DataItemCollection::tryAdditionalItemRegistration(std::shared_ptr<xmodel::Core::IDataItem>) const’:
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: error: no matching function for call to ‘bind(<unresolved overloaded function type>, const std::_Placeholder<1>&, const QUuid&)’
       , std::bind(&IDataItemCollectionScope::findItemById, _1, id)
                                                                  ^
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: note: candidates are:
In file included from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/bits/stl_algo.h:66:0,
                 from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/algorithm:62,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qglobal.h:68,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qatomic.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qhash.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/QHash:1,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/rappserv/code/include/convenience/stdhash_quuid.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/ItemId.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItem.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/DataItemDescriptor.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:9:
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1655:5: note: template<class _Func, class ... _BoundArgs> typename std::_Bind_helper<std::__or_<std::is_integral<typename std::decay<_Tp>::type>, std::is_enum<typename std::decay<_Tp>::type> >::value, _Func, _BoundArgs ...>::type std::bind(_Func&&, _BoundArgs&& ...)
     bind(_Func&& __f, _BoundArgs&&... __args)
     ^
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1655:5: note:   template argument deduction/substitution failed:
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: note:   couldn't deduce template parameter ‘_Func’
       , std::bind(&IDataItemCollectionScope::findItemById, _1, id)
                                                                  ^
In file included from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/bits/stl_algo.h:66:0,
                 from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/algorithm:62,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qglobal.h:68,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qatomic.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qhash.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/QHash:1,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/rappserv/code/include/convenience/stdhash_quuid.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/ItemId.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItem.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/DataItemDescriptor.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:9:
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1682:5: note: template<class _Result, class _Func, class ... _BoundArgs> typename std::_Bindres_helper<_Result, _Func, _BoundArgs>::type std::bind(_Func&&, _BoundArgs&& ...)
     bind(_Func&& __f, _BoundArgs&&... __args)
     ^
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1682:5: note:   template argument deduction/substitution failed:
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: note:   couldn't deduce template parameter ‘_Result’
       , std::bind(&IDataItemCollectionScope::findItemById, _1, id)
                                                                  ^
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:417:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^

This one is not even so bad, actually, as there are no macro expansions involved (we use Boost.Preprocessor as well). Still, it's awfully difficult to tell at a glance that this output is about two problems, the second one on the last 3 lines and the first one taking up the entire wall of text before that.

Is there a way to get some separator inserted between them? Even a blank line would do, something you could Search or grep for.

I've read the GCC docs on Options to Control Diagnostic Messages Formatting, but I couldn't find anything. [ is also not usable as a search anchor, because not all the messages have one (the first one above doesn't). I'm out of ideas.

Answer 1

Analysis

I am using some code that someone else wrote (debugging for another question on SO, to be precise), and I suppressed the -Werror option to get warnings:

$ gcc -O3 -g -std=c11 -Wall -Wextra stl.c -o stl
stl.c: In function ‘printStudent’:
stl.c:84:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Wformat=]
     printf("Name: %s ", student->first);
     ^
stl.c:84:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Wformat=]
stl.c:85:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
     printf("Grade: %s\n", student->grade);
     ^
stl.c:85:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
$

and enabled -Werror to get error messages:

$ gcc -O3 -g -std=c11 -Wall -Wextra -Werror stl.c -o stl
stl.c: In function ‘printStudent’:
stl.c:84:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Werror=format=]
     printf("Name: %s ", student->first);
     ^
stl.c:84:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Werror=format=]
stl.c:85:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Werror=format=]
     printf("Grade: %s\n", student->grade);
     ^
stl.c:85:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Werror=format=]
cc1: all warnings being treated as errors
$

You get some 'context messages', like the In function messages, but each individual warning starts with <source file>:<line>:<col>: warning:, and each error starts with a line containing error in place of warning. It continues to the next context message, or the next warning or error message, or the final summary line ('all warnings being treated as errors'). If you have extra information being produced (-H, or -v options), then life is more complex, but for routine compilations, that covers it.

In your rather more extensive C++ example, you have a context message plus two errors, with multiple notes to explain why the first error was produced.

Synthesis

It would, therefore, be possible to split up the messages with a suitable marker. In fact, it can be done fairly easily with a simple sed script:

#!/bin/sh
#
# Insert markers before GCC warning and error messages

sed -e '
/^.*:[1-9][0-9]*:[1-9][0-9]*: warning: /i\
\
-- WARNING --\
\

/^.*:[1-9][0-9]*:[1-9][0-9]*: error: /i\
\
-- ERROR --\
\
' "$@"

The script spotted the second error in your diagnostic output, which I'd missed on my first glance through.

Example

Here's some composite output from your example and mine (plus unexpurgated compilation command lines, miscellaneous):

/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp: In member function ‘virtual bool xmodel::Core::DataItemCollection::tryAdditionalItemRegistration(std::shared_ptr<xmodel::Core::IDataItem>) const’:

-- ERROR --

/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: error: no matching function for call to ‘bind(<unresolved overloaded function type>, const std::_Placeholder<1>&, const QUuid&)’
       , std::bind(&IDataItemCollectionScope::findItemById, _1, id)
                                                                  ^
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: note: candidates are:
In file included from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/bits/stl_algo.h:66:0,
                 from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/algorithm:62,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qglobal.h:68,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qatomic.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qhash.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/QHash:1,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/rappserv/code/include/convenience/stdhash_quuid.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/ItemId.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItem.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/DataItemDescriptor.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:9:
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1655:5: note: template<class _Func, class ... _BoundArgs> typename std::_Bind_helper<std::__or_<std::is_integral<typename std::decay<_Tp>::type>, std::is_enum<typename std::decay<_Tp>::type> >::value, _Func, _BoundArgs ...>::type std::bind(_Func&&, _BoundArgs&& ...)
     bind(_Func&& __f, _BoundArgs&&... __args)
     ^
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1655:5: note:   template argument deduction/substitution failed:
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: note:   couldn't deduce template parameter ‘_Func’
       , std::bind(&IDataItemCollectionScope::findItemById, _1, id)
                                                                  ^
In file included from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/bits/stl_algo.h:66:0,
                 from /gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/algorithm:62,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qglobal.h:68,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qatomic.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/qhash.h:45,
                 from /gl-sync/thirdparty/Qt/4.8.4/lnx_x23.64/include/QtCore/QHash:1,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/rappserv/code/include/convenience/stdhash_quuid.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/ItemId.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItem.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/DataItemDescriptor.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/include/xmodel/core/IDataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.h:11,
                 from /usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:9:
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1682:5: note: template<class _Result, class _Func, class ... _BoundArgs> typename std::_Bindres_helper<_Result, _Func, _BoundArgs>::type std::bind(_Func&&, _BoundArgs&& ...)
     bind(_Func&& __f, _BoundArgs&&... __args)
     ^
/gl-sync/compilers/gcc/4.8.2/sle11sp0/include/c++/4.8.2/functional:1682:5: note:   template argument deduction/substitution failed:
/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:414:66: note:   couldn't deduce template parameter ‘_Result’
       , std::bind(&IDataItemCollectionScope::findItemById, _1, id)
                                                                  ^

-- ERROR --

/usr2/viewstore_some/xy01/xy01_unix1/fubar/extensions/xmodel/core/code/src/DataItemCollection.cpp:417:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
'stl' is up to date.
    gcc -O3   -g   -I/Users/jleffler/inc   -std=c11   -Wall -Wextra -Wmissing-prototypes -Wstrict-prototypes -Wold-style-definition     stl.c -o stl -L/Users/jleffler/lib/64 -ljl
    gcc -O3   -g   -I/Users/jleffler/inc   -std=c11   -Wall -Wextra -Wmissing-prototypes -Wstrict-prototypes -Wold-style-definition     stl.c -o stl -L/Users/jleffler/lib/64 -ljl
stl.c: In function ‘printStudent’:

-- WARNING --

stl.c:84:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Wformat=]
     printf("Name: %s ", student->first);
     ^

-- WARNING --

stl.c:84:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Wformat=]

-- WARNING --

stl.c:85:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
     printf("Grade: %s\n", student->grade);
     ^

-- WARNING --

stl.c:85:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
    gcc -O3   -g   -I/Users/jleffler/inc   -std=c11   -Wall -Wextra -Wmissing-prototypes -Wstrict-prototypes -Wold-style-definition -Werror    stl.c -o stl -L/Users/jleffler/lib/64 -ljl
stl.c: In function ‘printStudent’:

-- ERROR --

stl.c:84:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Werror=format=]
     printf("Name: %s ", student->first);
     ^

-- ERROR --

stl.c:84:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘List’ [-Werror=format=]

-- ERROR --

stl.c:85:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Werror=format=]
     printf("Grade: %s\n", student->grade);
     ^

-- ERROR --

stl.c:85:5: error: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Werror=format=]
cc1: all warnings being treated as errors