Telling gcc diagnostics apart

Question 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

Question 2

You could try vim and its quickfix functionality. I don't know how familiar you are with vim, but its :make command runs the build and catches the resulting errors, and then with :cnext (or the shorter :cn) you iterate through all errors and the editor jumps to the file+line containing the error. There are many other functionalities documented in the link above but that's basically the gist of it.

Question 3

There are multiple solutions to your problem.

The first thing to ask is, are you willing to upgrade GCC to 4.9? If yes, that is great, because GCC 4.9 natively supports diagnostic output coloring with:

-fdiagnostics-color[=WHEN]
-fno-diagnostics-color

You can find more information about usage here.

On the other hand, if you want o stick with GCC 4.8.2, you have the following options:

colorGCC

colorgcc is a Perl script written by Jamie Moyers to colorize the terminal output of GCC so error messages can be found within longer compiler outputs.
GilCC

GilCC is a Ruby program that will colorize the output from any compiler such as GCC. So if you are a GCC user you probably realized that it is very hard to tell "warnings" and "errors" from other texts. GilCC was written to resolve this issue.
gccfilter (aimed more for g++)

gccfilter is a filter to colorize and simplify (or expand) gcc diagnostic messages. gccfilter is particularly aimed at g++ (i.e. regarding C++) messages which can contain lot of template-related errors or warnings difficult to understand.