I'm working on an existing C++ codebase that happens to use SIZE_MAX in a couple of places. I did some refactoring and now SIZE_MAX is not defined in one of the modules. This problem appeared when Travis-CI attempted to build the project on Linux. It worked fine before I refactored stuff, but tracing which exact header files were included is difficult.
In an attempt to replicate the problem locally, I installed an Ubuntu VM with the default gcc and was able to reproduce it. Here's the relevant source:
#include <stddef.h>
int main()
{
size_t a = SIZE_MAX;
}
The command line is simply:
g++ a.cpp
The error is:
a.cpp: In function ‘int main()’:
a.cpp:5:16: error: ‘SIZE_MAX’ was not declared in this scope
System info:
$ uname -a
Linux quartz 3.11.0-15-generic #25~precise1-Ubuntu SMP Thu Jan 30 17:39:31 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
$ gcc --version
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
I have tried including cstdint, stdint.h, limits.h, inttypes.h, stdio.h, stdlib.h, and probably some others, and I can't figure out which specific header file I need for SIZE_MAX.
It is important to note that the program I'm working on compiled fine, with SIZE_MAX used in various places, before I made some changes. The changes I made caused it to become undefined in one .cpp source file where it was used (the others continue to be fine). So there exists some header file on my system where it is correctly defined.
It's likely that some header defined __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS before stdint.h was included.
Compiling on Linux with g++ -D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS a.cpp should fix this issue on the older compilers.
If you'd like to learn more about these macros...
18.4.1 Header <cstdint> synopsis
The header also defines numerous macros of the form:
INT_[FAST LEAST]{8 16 32 64}_MIN
[U]INT_[FAST LEAST]{8 16 32 64}_MAX
INT{MAX PTR}_MIN
[U]INT{MAX PTR}_MAX
{PTRDIFF SIG_ATOMIC WCHAR WINT}{_MAX _MIN}
SIZE_MAX
EDIT
In the current C++11/14 standard, SIZE_MAX is introduced and mentioned only in <cstdint>. It is also part of C99, of which specification C++11 fully includes via the <cxxx> headers. So it seems it was not defined prior to C++11.
Which C++ standard header defines SIZE_MAX?
Its supposed to be defined in <cstdint>, but its optional.
Here are the results on Fedora 22 with GCC 5.1:
#include <cstdint>
// use SIZE_MAX
Results in:
g++ -DNDEBUG -g -O2 -fPIC -march=native -pipe -c filters.cpp
In file included from /usr/include/c++/5.1.1/cstdint:35:0,
from filters.cpp:14:
/usr/include/c++/5.1.1/bits/c++0x_warning.h:32:2: error: #error This file requires
compiler and library support for the ISO C++ 2011 standard. This support is currently
experimental, and must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
#error This file requires compiler and library support for the \
^
filters.cpp: In constructor ‘Filter::Filter(BufferedTransformation*)’:
filters.cpp:305:36: error: ‘SIZE_MAX’ was not declared in this scope
: Filter(attachment), m_firstSize(SIZE_MAX), m_blockSize(0), m_lastSize(SIZE_M
^
It was simply easier to do the following, and stop worrying about non-portable optional-ness that still causes problems in 2015.
#include <limits>
#ifndef SIZE_MAX
# ifdef __SIZE_MAX__
# define SIZE_MAX __SIZE_MAX__
# else
# define SIZE_MAX std::numeric_limits<size_t>::max()
# endif
#endif
Trying __SIZE_MAX__ gets you back to the compile time constant that you probably crave. You can see if its defined in the preprocessor with cpp -dM < /dev/null | grep __SIZE_MAX__.
(And how/why numeric_limits<size_t>::max() is not a compile time constant is another C++ mystery, but that's a different problem).
Related
What is the difference between g++ and gcc? Which one of them should be used for general c++ development?
gcc and g++ are compiler-drivers of the GNU Compiler Collection (which was once upon a time just the GNU C Compiler).
Even though they automatically determine which backends (cc1 cc1plus ...) to call depending on the file-type, unless overridden with -x language, they have some differences.
The probably most important difference in their defaults is which libraries they link against automatically.
According to GCC's online documentation link options and how g++ is invoked, g++ is equivalent to gcc -xc++ -lstdc++ -shared-libgcc (the 1st is a compiler option, the 2nd two are linker options). This can be checked by running both with the -v option (it displays the backend toolchain commands being run).
GCC: GNU Compiler Collection
Referrers to all the different languages that are supported by the GNU compiler.
gcc: GNU C Compiler
g++: GNU C++ Compiler
The main differences:
gcc will compile: *.c\*.cpp files as C and C++ respectively.
g++ will compile: *.c\*.cpp files but they will all be treated as C++ files.
Also if you use g++ to link the object files it automatically links in the std C++ libraries (gcc does not do this).
gcc compiling C files has fewer predefined macros.
gcc compiling *.cpp and g++ compiling *.c\*.cpp files has a few extra macros.
Extra Macros when compiling *.cpp files:
#define __GXX_WEAK__ 1
#define __cplusplus 1
#define __DEPRECATED 1
#define __GNUG__ 4
#define __EXCEPTIONS 1
#define __private_extern__ extern
For c++ you should use g++.
It's the same compiler (e.g. the GNU compiler collection). GCC or G++ just choose a different front-end with different default options.
In a nutshell: if you use g++ the frontend will tell the linker that you may want to link with the C++ standard libraries. The gcc frontend won't do that (also it could link with them if you pass the right command line options).
What is the difference between g++ and gcc?
gcc has evolved from a single language "GNU C Compiler" to be a multi-language "GNU Compiler Collection". The term gcc may still sometimes refer to the "GNU C Compiler" in the context of C programming.
man gcc
# GCC(1) GNU
#
# NAME
# gcc - GNU project C and C++ compiler
However, g++ is the C++ compiler for the GNU Compiler Collection. Like gnat is the Ada compiler for gcc. see Using the GNU Compiler Collection (GCC)
For example, the Ubuntu 16.04 and 18.04 man g++ command returns the GCC(1) manual page.
The Ubuntu 16.04 and 18.04 man gcc states that ...
g++ accepts mostly the same options as gcc
and that the default ...
... use of gcc does not add the C++ library. g++ is a program
that calls GCC and automatically specifies linking against the C++
library. It treats .c, .h and .i files as C++ source files instead of
C source files unless -x is used. This program is also useful when
precompiling a C header file with a .h extension for use in C++
compilations.
Search the gcc man pages for more details on the option variances between gcc and g++.
Which one should be used for general c++ development?
Technically, either gcc or g++ can be used for general C++ development with applicable option settings. However, the g++ default behavior is naturally aligned to a C++ development.
The Ubuntu 18.04 'gcc' man page added, and Ubuntu 20.04 continues to have, the following paragraph:
The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-compiling, or machine-gcc-version to run a specific version of GCC. When you compile C++ programs, you should invoke GCC as g++ instead.
Side Note: In the case of the Xcode.app embedded toolchain, g++ simply links to gcc. Thus, g++ invocations may vary on a per-toolchain basis.
ls -l /Applications/Xcode.app/Contents/Developer/usr/bin
# …
# lrwxr-xr-x 1 root wheel 3 Apr 27 2021 g++ -> gcc
# -rwxr-xr-x 1 root wheel 167120 Nov 23 20:51 gcc
### -- versus --
which -a g++
# /usr/bin/g++
ls -l /usr/bin/g++
# -rwxr-xr-x 1 root wheel 137616 Jan 1 2020 /usr/bin/g++
One notable difference is that if you pass a .c file to gcc it will compile as C.
The default behavior of g++ is to treat .c files as C++ (unless -x c is specified).
Although the gcc and g++ commands do very similar things, g++ is designed to be the command you'd invoke to compile a C++ program; it's intended to automatically do the right thing.
Behind the scenes, they're really the same program. As I understand, both decide whether to compile a program as C or as C++ based on the filename extension. Both are capable of linking against the C++ standard library, but only g++ does this by default. So if you have a program written in C++ that doesn't happen to need to link against the standard library, gcc will happen to do the right thing; but then, so would g++. So there's really no reason not to use g++ for general C++ development.
I became interested in the issue and perform some experiments
I found that description here, but it is very short.
Then I tried to experiment with gcc.exe and g++.exe on my windows machine:
$ g++ --version | head -n1
g++.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3
$ gcc --version | head -n1
gcc.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3
I tried to compile c89, c99, and c++1998 simple test files and It's work well for me with correct extensions matching for language
gcc -std=c99 test_c99.c
gcc -std=c89 test_c89.c
g++ -std=c++98 test_cpp.cpp
gcc -std=c++98 test_cpp.cpp
But when I try to run "gnu compiler collection" tool in that fashion:
$ gcc -std=c++98 test_cpp.c
cc1.exe: warning: command line option '-std=c++98' is valid for C++/ObjC++ but not for C [enabled by default]
But this one still work with no errors
$ gcc -x c++ -std=c++98 test_cpp.c
And this also
$ g++ -std=c++0x test_cpp_11.cpp
p.s. Test files
$ cat test_c89.c test_c99.c test_cpp.cpp
// C89 compatible file
int main()
{
int x[] = {0, 2};
return sizeof(x);
}
// C99 compatible file
int main()
{
int x[] = {[1]=2};
return sizeof(x);
}
// C++1998,2003 compatible file
class X{};
int main()
{
X x;
return sizeof(x);
}
// C++11
#include <vector>
enum class Color : int{red,green,blue}; // scoped enum
int main()
{
std::vector<int> a {1,2,3}; // bracket initialization
return 0;
}
Findings:
If look at process tree then it seems that gcc, and g++ is backend to other tools, which in my environment are: cc1plus.exe, cc1.exe, collect2.exe, as.exe, ld.exe
gcc works fine as metatool for if you have correct extension or set correct
-std -x flags. See this
“GCC” is a common shorthand term for the GNU Compiler Collection. This is both the most general name for the compiler, and the name used when the emphasis is on compiling C programs (as the abbreviation formerly stood for “GNU C Compiler”).
When referring to C++ compilation, it is usual to call the compiler “G++”. Since there is only one compiler, it is also accurate to call it “GCC” no matter what the language context; however, the term “G++” is more useful when the emphasis is on compiling C++ programs.
You could read more here.
I was testing gcc and g++ in a linux system. By using MAKEFILE, I can define the compliler used by "GNU make". I tested with the so called "dynamic memory" locating feature of "C plus plus" by :
int main(){
int * myptr = new int;
* myptr = 1;
printf("myptr[0] is %i\n",*myptr);
return 0;
}
Only g++ can successfully compile on my computer while gcc will report error
undefined reference to `operator new(unsigned long)'
So my own conclusion is gcc does not fully support "C plus plus". It seems that choosing g++ for C++ source files is a better option.
gcc and g ++ are both GNU compiler. They both compile c and c++. The difference is for *.c files gcc treats it as a c program, and g++ sees it as a c ++ program. *.cpp files are considered to be c ++ programs. c++ is a super set of c and the syntax is more strict, so be careful about the suffix.
What is the difference between g++ and gcc? Which one of them should be used for general c++ development?
gcc and g++ are compiler-drivers of the GNU Compiler Collection (which was once upon a time just the GNU C Compiler).
Even though they automatically determine which backends (cc1 cc1plus ...) to call depending on the file-type, unless overridden with -x language, they have some differences.
The probably most important difference in their defaults is which libraries they link against automatically.
According to GCC's online documentation link options and how g++ is invoked, g++ is equivalent to gcc -xc++ -lstdc++ -shared-libgcc (the 1st is a compiler option, the 2nd two are linker options). This can be checked by running both with the -v option (it displays the backend toolchain commands being run).
GCC: GNU Compiler Collection
Referrers to all the different languages that are supported by the GNU compiler.
gcc: GNU C Compiler
g++: GNU C++ Compiler
The main differences:
gcc will compile: *.c\*.cpp files as C and C++ respectively.
g++ will compile: *.c\*.cpp files but they will all be treated as C++ files.
Also if you use g++ to link the object files it automatically links in the std C++ libraries (gcc does not do this).
gcc compiling C files has fewer predefined macros.
gcc compiling *.cpp and g++ compiling *.c\*.cpp files has a few extra macros.
Extra Macros when compiling *.cpp files:
#define __GXX_WEAK__ 1
#define __cplusplus 1
#define __DEPRECATED 1
#define __GNUG__ 4
#define __EXCEPTIONS 1
#define __private_extern__ extern
For c++ you should use g++.
It's the same compiler (e.g. the GNU compiler collection). GCC or G++ just choose a different front-end with different default options.
In a nutshell: if you use g++ the frontend will tell the linker that you may want to link with the C++ standard libraries. The gcc frontend won't do that (also it could link with them if you pass the right command line options).
What is the difference between g++ and gcc?
gcc has evolved from a single language "GNU C Compiler" to be a multi-language "GNU Compiler Collection". The term gcc may still sometimes refer to the "GNU C Compiler" in the context of C programming.
man gcc
# GCC(1) GNU
#
# NAME
# gcc - GNU project C and C++ compiler
However, g++ is the C++ compiler for the GNU Compiler Collection. Like gnat is the Ada compiler for gcc. see Using the GNU Compiler Collection (GCC)
For example, the Ubuntu 16.04 and 18.04 man g++ command returns the GCC(1) manual page.
The Ubuntu 16.04 and 18.04 man gcc states that ...
g++ accepts mostly the same options as gcc
and that the default ...
... use of gcc does not add the C++ library. g++ is a program
that calls GCC and automatically specifies linking against the C++
library. It treats .c, .h and .i files as C++ source files instead of
C source files unless -x is used. This program is also useful when
precompiling a C header file with a .h extension for use in C++
compilations.
Search the gcc man pages for more details on the option variances between gcc and g++.
Which one should be used for general c++ development?
Technically, either gcc or g++ can be used for general C++ development with applicable option settings. However, the g++ default behavior is naturally aligned to a C++ development.
The Ubuntu 18.04 'gcc' man page added, and Ubuntu 20.04 continues to have, the following paragraph:
The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-compiling, or machine-gcc-version to run a specific version of GCC. When you compile C++ programs, you should invoke GCC as g++ instead.
Side Note: In the case of the Xcode.app embedded toolchain, g++ simply links to gcc. Thus, g++ invocations may vary on a per-toolchain basis.
ls -l /Applications/Xcode.app/Contents/Developer/usr/bin
# …
# lrwxr-xr-x 1 root wheel 3 Apr 27 2021 g++ -> gcc
# -rwxr-xr-x 1 root wheel 167120 Nov 23 20:51 gcc
### -- versus --
which -a g++
# /usr/bin/g++
ls -l /usr/bin/g++
# -rwxr-xr-x 1 root wheel 137616 Jan 1 2020 /usr/bin/g++
One notable difference is that if you pass a .c file to gcc it will compile as C.
The default behavior of g++ is to treat .c files as C++ (unless -x c is specified).
Although the gcc and g++ commands do very similar things, g++ is designed to be the command you'd invoke to compile a C++ program; it's intended to automatically do the right thing.
Behind the scenes, they're really the same program. As I understand, both decide whether to compile a program as C or as C++ based on the filename extension. Both are capable of linking against the C++ standard library, but only g++ does this by default. So if you have a program written in C++ that doesn't happen to need to link against the standard library, gcc will happen to do the right thing; but then, so would g++. So there's really no reason not to use g++ for general C++ development.
I became interested in the issue and perform some experiments
I found that description here, but it is very short.
Then I tried to experiment with gcc.exe and g++.exe on my windows machine:
$ g++ --version | head -n1
g++.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3
$ gcc --version | head -n1
gcc.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3
I tried to compile c89, c99, and c++1998 simple test files and It's work well for me with correct extensions matching for language
gcc -std=c99 test_c99.c
gcc -std=c89 test_c89.c
g++ -std=c++98 test_cpp.cpp
gcc -std=c++98 test_cpp.cpp
But when I try to run "gnu compiler collection" tool in that fashion:
$ gcc -std=c++98 test_cpp.c
cc1.exe: warning: command line option '-std=c++98' is valid for C++/ObjC++ but not for C [enabled by default]
But this one still work with no errors
$ gcc -x c++ -std=c++98 test_cpp.c
And this also
$ g++ -std=c++0x test_cpp_11.cpp
p.s. Test files
$ cat test_c89.c test_c99.c test_cpp.cpp
// C89 compatible file
int main()
{
int x[] = {0, 2};
return sizeof(x);
}
// C99 compatible file
int main()
{
int x[] = {[1]=2};
return sizeof(x);
}
// C++1998,2003 compatible file
class X{};
int main()
{
X x;
return sizeof(x);
}
// C++11
#include <vector>
enum class Color : int{red,green,blue}; // scoped enum
int main()
{
std::vector<int> a {1,2,3}; // bracket initialization
return 0;
}
Findings:
If look at process tree then it seems that gcc, and g++ is backend to other tools, which in my environment are: cc1plus.exe, cc1.exe, collect2.exe, as.exe, ld.exe
gcc works fine as metatool for if you have correct extension or set correct
-std -x flags. See this
“GCC” is a common shorthand term for the GNU Compiler Collection. This is both the most general name for the compiler, and the name used when the emphasis is on compiling C programs (as the abbreviation formerly stood for “GNU C Compiler”).
When referring to C++ compilation, it is usual to call the compiler “G++”. Since there is only one compiler, it is also accurate to call it “GCC” no matter what the language context; however, the term “G++” is more useful when the emphasis is on compiling C++ programs.
You could read more here.
I was testing gcc and g++ in a linux system. By using MAKEFILE, I can define the compliler used by "GNU make". I tested with the so called "dynamic memory" locating feature of "C plus plus" by :
int main(){
int * myptr = new int;
* myptr = 1;
printf("myptr[0] is %i\n",*myptr);
return 0;
}
Only g++ can successfully compile on my computer while gcc will report error
undefined reference to `operator new(unsigned long)'
So my own conclusion is gcc does not fully support "C plus plus". It seems that choosing g++ for C++ source files is a better option.
gcc and g ++ are both GNU compiler. They both compile c and c++. The difference is for *.c files gcc treats it as a c program, and g++ sees it as a c ++ program. *.cpp files are considered to be c ++ programs. c++ is a super set of c and the syntax is more strict, so be careful about the suffix.
What is the difference between g++ and gcc? Which one of them should be used for general c++ development?
gcc and g++ are compiler-drivers of the GNU Compiler Collection (which was once upon a time just the GNU C Compiler).
Even though they automatically determine which backends (cc1 cc1plus ...) to call depending on the file-type, unless overridden with -x language, they have some differences.
The probably most important difference in their defaults is which libraries they link against automatically.
According to GCC's online documentation link options and how g++ is invoked, g++ is equivalent to gcc -xc++ -lstdc++ -shared-libgcc (the 1st is a compiler option, the 2nd two are linker options). This can be checked by running both with the -v option (it displays the backend toolchain commands being run).
GCC: GNU Compiler Collection
Referrers to all the different languages that are supported by the GNU compiler.
gcc: GNU C Compiler
g++: GNU C++ Compiler
The main differences:
gcc will compile: *.c\*.cpp files as C and C++ respectively.
g++ will compile: *.c\*.cpp files but they will all be treated as C++ files.
Also if you use g++ to link the object files it automatically links in the std C++ libraries (gcc does not do this).
gcc compiling C files has fewer predefined macros.
gcc compiling *.cpp and g++ compiling *.c\*.cpp files has a few extra macros.
Extra Macros when compiling *.cpp files:
#define __GXX_WEAK__ 1
#define __cplusplus 1
#define __DEPRECATED 1
#define __GNUG__ 4
#define __EXCEPTIONS 1
#define __private_extern__ extern
For c++ you should use g++.
It's the same compiler (e.g. the GNU compiler collection). GCC or G++ just choose a different front-end with different default options.
In a nutshell: if you use g++ the frontend will tell the linker that you may want to link with the C++ standard libraries. The gcc frontend won't do that (also it could link with them if you pass the right command line options).
What is the difference between g++ and gcc?
gcc has evolved from a single language "GNU C Compiler" to be a multi-language "GNU Compiler Collection". The term gcc may still sometimes refer to the "GNU C Compiler" in the context of C programming.
man gcc
# GCC(1) GNU
#
# NAME
# gcc - GNU project C and C++ compiler
However, g++ is the C++ compiler for the GNU Compiler Collection. Like gnat is the Ada compiler for gcc. see Using the GNU Compiler Collection (GCC)
For example, the Ubuntu 16.04 and 18.04 man g++ command returns the GCC(1) manual page.
The Ubuntu 16.04 and 18.04 man gcc states that ...
g++ accepts mostly the same options as gcc
and that the default ...
... use of gcc does not add the C++ library. g++ is a program
that calls GCC and automatically specifies linking against the C++
library. It treats .c, .h and .i files as C++ source files instead of
C source files unless -x is used. This program is also useful when
precompiling a C header file with a .h extension for use in C++
compilations.
Search the gcc man pages for more details on the option variances between gcc and g++.
Which one should be used for general c++ development?
Technically, either gcc or g++ can be used for general C++ development with applicable option settings. However, the g++ default behavior is naturally aligned to a C++ development.
The Ubuntu 18.04 'gcc' man page added, and Ubuntu 20.04 continues to have, the following paragraph:
The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-compiling, or machine-gcc-version to run a specific version of GCC. When you compile C++ programs, you should invoke GCC as g++ instead.
Side Note: In the case of the Xcode.app embedded toolchain, g++ simply links to gcc. Thus, g++ invocations may vary on a per-toolchain basis.
ls -l /Applications/Xcode.app/Contents/Developer/usr/bin
# …
# lrwxr-xr-x 1 root wheel 3 Apr 27 2021 g++ -> gcc
# -rwxr-xr-x 1 root wheel 167120 Nov 23 20:51 gcc
### -- versus --
which -a g++
# /usr/bin/g++
ls -l /usr/bin/g++
# -rwxr-xr-x 1 root wheel 137616 Jan 1 2020 /usr/bin/g++
One notable difference is that if you pass a .c file to gcc it will compile as C.
The default behavior of g++ is to treat .c files as C++ (unless -x c is specified).
Although the gcc and g++ commands do very similar things, g++ is designed to be the command you'd invoke to compile a C++ program; it's intended to automatically do the right thing.
Behind the scenes, they're really the same program. As I understand, both decide whether to compile a program as C or as C++ based on the filename extension. Both are capable of linking against the C++ standard library, but only g++ does this by default. So if you have a program written in C++ that doesn't happen to need to link against the standard library, gcc will happen to do the right thing; but then, so would g++. So there's really no reason not to use g++ for general C++ development.
I became interested in the issue and perform some experiments
I found that description here, but it is very short.
Then I tried to experiment with gcc.exe and g++.exe on my windows machine:
$ g++ --version | head -n1
g++.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3
$ gcc --version | head -n1
gcc.exe (gcc-4.6.3 release with patches [build 20121012 by perlmingw.sf.net]) 4.6.3
I tried to compile c89, c99, and c++1998 simple test files and It's work well for me with correct extensions matching for language
gcc -std=c99 test_c99.c
gcc -std=c89 test_c89.c
g++ -std=c++98 test_cpp.cpp
gcc -std=c++98 test_cpp.cpp
But when I try to run "gnu compiler collection" tool in that fashion:
$ gcc -std=c++98 test_cpp.c
cc1.exe: warning: command line option '-std=c++98' is valid for C++/ObjC++ but not for C [enabled by default]
But this one still work with no errors
$ gcc -x c++ -std=c++98 test_cpp.c
And this also
$ g++ -std=c++0x test_cpp_11.cpp
p.s. Test files
$ cat test_c89.c test_c99.c test_cpp.cpp
// C89 compatible file
int main()
{
int x[] = {0, 2};
return sizeof(x);
}
// C99 compatible file
int main()
{
int x[] = {[1]=2};
return sizeof(x);
}
// C++1998,2003 compatible file
class X{};
int main()
{
X x;
return sizeof(x);
}
// C++11
#include <vector>
enum class Color : int{red,green,blue}; // scoped enum
int main()
{
std::vector<int> a {1,2,3}; // bracket initialization
return 0;
}
Findings:
If look at process tree then it seems that gcc, and g++ is backend to other tools, which in my environment are: cc1plus.exe, cc1.exe, collect2.exe, as.exe, ld.exe
gcc works fine as metatool for if you have correct extension or set correct
-std -x flags. See this
“GCC” is a common shorthand term for the GNU Compiler Collection. This is both the most general name for the compiler, and the name used when the emphasis is on compiling C programs (as the abbreviation formerly stood for “GNU C Compiler”).
When referring to C++ compilation, it is usual to call the compiler “G++”. Since there is only one compiler, it is also accurate to call it “GCC” no matter what the language context; however, the term “G++” is more useful when the emphasis is on compiling C++ programs.
You could read more here.
I was testing gcc and g++ in a linux system. By using MAKEFILE, I can define the compliler used by "GNU make". I tested with the so called "dynamic memory" locating feature of "C plus plus" by :
int main(){
int * myptr = new int;
* myptr = 1;
printf("myptr[0] is %i\n",*myptr);
return 0;
}
Only g++ can successfully compile on my computer while gcc will report error
undefined reference to `operator new(unsigned long)'
So my own conclusion is gcc does not fully support "C plus plus". It seems that choosing g++ for C++ source files is a better option.
gcc and g ++ are both GNU compiler. They both compile c and c++. The difference is for *.c files gcc treats it as a c program, and g++ sees it as a c ++ program. *.cpp files are considered to be c ++ programs. c++ is a super set of c and the syntax is more strict, so be careful about the suffix.
I am trying to port an ARM-C library to be compiled with x86_64 C++, and I am getting the following error:
In file included from /usr/include/c++/5/cwchar:44:0,
from /usr/include/c++/5/bits/postypes.h:40,
from /usr/include/c++/5/bits/char_traits.h:40,
from /usr/include/c++/5/string:40,
from MyFile.h:19,
/usr/include/wchar.h:226:20: error: initializer provided for function
__THROW __asm ("wcschr") __attribute_pure__;
^
where MyFile.h has the following structure
// comments
#pragma once
// comments
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string> //<<< line 19
…
Initially, instead of it used to be which gave me a similar error:
In file included from MyFile.h:19:
/usr/include/string.h:73:21: error: initializer provided for function
__THROW __asm ("memchr") __attribute_pure__ __nonnull ((1));
^
Compiler version:
GNU C++14 (Ubuntu 5.4.0-6ubuntu1~16.04.11) version 5.4.0 20160609 (x86_64-linux-gnu)
compiled by GNU C version 5.4.0 20160609, GMP version 6.1.0, MPFR version 3.1.4, MPC version 1.0.3
ldd (Ubuntu GLIBC 2.23-0ubuntu11) 2.23
Compilation flags:
#g++ -O3 -std=c++14 -fpermissive -Wno-system-headers -w
UPDATE 1:
I've been modifying the Makefile, and the original version contains $#.via. For instance:
#$(COMPILE) -M -MF $(subst .o,.d.tmp,$#) -MT $# -E $(C_FLAGS) $#.via $< -o $#.preprocessed.c
and I changed the $#.via for #$#.via because I saw that in an older project they did it like that. However, if I leave as $#.via I just get:
SomeFile.c:1:1 fatal error: OneHeader.h: No such file or directory
I am starting to think that my Makefile is somewhere wrong...
I misunderstood the compiler option... Few lines above, my makefile creates the #.via files passing DEFINES and INCLUDES
#echo $(patsubst %, '%', $(C_DEFINES)) > $#.via
#echo $(C_INCLUDE) >> $#.via
and those #.via files are passed as additional arguments for the compilation. While for armcc the --via is supported see here, I found that for g++ -according to the gcc doc- the syntax is #<your_file>. Thus, what #$#.via does is simply to parse the $#.via to <your_file>.via.
Now I am still getting the initializer provided for function error message.
UPDATE 2:
I found the problem and I explained what happened in the answer section. See below.
Root cause
The problem was originated because I redefined __asm to be replaced by nothing (e.g. #define __asm) since I didn't want to touch the assembly code yet. Remember that I said I am porting ARM to x86, so I thought that easiest way to get rid of the compile errors was to remove all those __asm instructions, but not considering the effects of doing such a thing.
In other words, when I included the string.h header, the header itself uses assembly call as the error messaged pointed out:
/usr/include/wchar.h:226:20: error: initializer provided for function
__THROW __asm ("wcschr") __attribute_pure__;
and when the preprocessor changed the __asm("wcschr") for ("wcschr") the compiler hits the error -- which makes sense.
Moral of the history
Do not redefine qualifiers since it will also affect other modules that you are not seeing directly and prefer creating a macro to just change them (e.g. __asm for /*__asm*/) or just run sed in you code base.
I am running into issues compiling Linux-bound applications in Cygwin.
This error:
error: ‘EOF’ was not declared in this scope
is produced by the following code snippet
if (option == EOF) break;
Compiling this in CentOS directly produces no errors.
These are the g++ params passed by the make file:
-g -O0 -Wall -Wextra -std=gnu++11
GCC version on centOS:
4.8.1 20130715
GCC version in Cygwin
4.8.2
I am wondering if I am just missing some libraries in Cygwin, or if this is just a limitation of Cygwin and can't be resolved.
EOF is defined in stdio.h / cstdio. What is likely happening is that you aren't including one of those headers, but are including, for example, iostream. Standard library headers are permitted to cause other headers to get included as well, and some implementations' iostream headers do exactly this, but not all. You shouldn't rely on it. If you use EOF, add an explicit include for the appropriate header in your own code. (Even if it isn't your code, which it isn't in this case, the modification required in the source code is the same.)