fichier d'entête lu plusieurs fois par g++

Version imprimable

bonjour,

voici le fichier d'entête:

Code:

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#ifndef tables_hpp
#define tables_hpp
 
#include <string>
 
std::string tableAdd[10][10]={
	{"0","1","2","3","4","5","6","7","8","9"},
	{"1","2","3","4","5","6","7","8","9","10"},
	{"2","3","4","5","6","7","8","9","10","11"},
	{"3","4","5","6","7","8","9","10","11","12"},
	{"4","5","6","7","8","9","10","11","12","13"},
	{"5","6","7","8","9","10","11","12","13","14"},
	{"6","7","8","9","10","11","12","13","14","15"},
	{"7","8","9","10","11","12","13","14","15","16"},
	{"8","9","10","11","12","13","14","15","16","17"},
	{"9","10","11","12","13","14","15","16","17","18"}
};
 
std::string tableAddRet[10][10]={
	{"1","2","3","4","5","6","7","8","9","10"},
	{"2","3","4","5","6","7","8","9","10","11"},
	{"3","4","5","6","7","8","9","10","11","12"},
	{"4","5","6","7","8","9","10","11","12","13"},
	{"5","6","7","8","9","10","11","12","13","14"},
	{"6","7","8","9","10","11","12","13","14","15"},
	{"7","8","9","10","11","12","13","14","15","16"},
	{"8","9","10","11","12","13","14","15","16","17"},
	{"9","10","11","12","13","14","15","16","17","18"},
	{"10","11","12","13","14","15","16","17","18","19"}
};
 
 
std::string tableMult[10][10]={
	{"0","0","0","0","0","0","0","0","0","0"},
	{"0","1","2","3","4","5","6","7","8","9"},
	{"0","2","4","6","8","10","12","14","16","18"},
	{"0","3","6","9","12","15","18","21","24","27"},
	{"0","4","8","12","16","20","24","28","32","36"},
	{"0","5","10","15","20","25","30","35","40","45"},
	{"0","6","12","18","24","30","36","42","48","54"},
	{"0","7","14","21","28","35","42","49","56","63"},
	{"0","8","16","24","32","40","48","56","64","72"},
	{"0","9","18","27","36","45","54","63","72","81"}
};
 
std::string tableSous[20][20]={
	{"0"},
	{"1","0"},
	{"2","1","0"},
	{"3","2","1","0"},
	{"4","3","2","1","0"},
	{"5","4","3","2","1","0"},
	{"6","5","4","3","2","1","0"},
	{"7","6","5","4","3","2","1","0"},
	{"8","7","6","5","4","3","2","1","0"},
	{"9","8","7","6","5","4","3","2","1","0"},
	{"10","9","8","7","6","5","4","3","2","1","0"},
	{"11","10","9","8","7","6","5","4","3","2","1","0"},
	{"12","11","10","9","8","7","6","5","4","3","2","1","0"},
	{"13","12","11","10","9","8","7","6","5","4","3","2","1","0"},
	{"14","13","12","11","10","9","8","7","6","5","4","3","2","1","0"},
	{"15","14","13","12","11","10","9","8","7","6","5","4","3","2","1","0"},
	{"16","15","14","13","12","11","10","9","8","7","6","5","4","3","2","1","0"},
	{"17","16","15","14","13","12","11","10","9","8","7","6","5","4","3","2","1","0"},
	{"18","17","16","15","14","13","12","11","10","9","8","7","6","5","4","3","2","1","0"},
	{"19","18","17","16","15","14","13","12","11","10","9","8","7","6","5","4","3","2","1","0"}
};
 
 
 
#endif

j'ai bien mis les directives

Code:

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#ifndef tables_hpp
#define tables_hpp
#endif

g++ me répond:

Code:

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/tmp/cc6qvIEd.o:(.bss+0x0): définitions multiples de « tableAdd »
/tmp/ccvYQNRP.o:(.bss+0x0): défini pour la première fois ici
/tmp/cc6qvIEd.o:(.bss+0x1c0): définitions multiples de « tableAddRet »
/tmp/ccvYQNRP.o:(.bss+0x1c0): défini pour la première fois ici
/tmp/cc6qvIEd.o:(.bss+0x380): définitions multiples de « tableMult »
/tmp/ccvYQNRP.o:(.bss+0x380): défini pour la première fois ici
/tmp/cc6qvIEd.o:(.bss+0x540): définitions multiples de « tableSous »
/tmp/ccvYQNRP.o:(.bss+0x540): défini pour la première fois ici
collect2: error: ld returned 1 exit status

quelqu'un a une idée?

04/08/2016, 07h48
Médinoc

Tu dois séparer la déclaration de la définition; cette dernière doit être dans un .cpp, alors que la déclaration reste dans le .h
04/08/2016, 08h43
emmesse

j'ai oublié de préciser que le nom du fichier est "tables.hpp"

il n'y a pas de fonctions (ni déclarations, ni définitions). Il n'y a que des tableaux initialisés.

je ne comprend vraiment pas.pourquoi ça fait ça.
04/08/2016, 08h55
Ehonn
En fait il s'agit des déclarations et définitions des variables :
Code:

1 2 3 4 5 6 // Déclaration /*extern*/ T t; // Définition t = T(); // Déclaration + Définition T t = T();
Pour la déclaration, il me semble que tu peux utiliser extern ou faire une variable static de classe.

Une autre solution, pour tout laisser dans le fichier d'entête, est de faire retourner ta variable par une fonction inline.
(En C++17, tu pourrais directement utiliser inline sur les variables.)
04/08/2016, 10h58
ternel

Ca va plus loin, sans le mot clé extern, même sans initialiseur, une variable est définie (éventuellement à une valeur arbitraire).

Il y a une alternative, l'inclure dans un namespace anonyme. Tu auras juste plusieurs copies, une dans chaque fichier incluant l'en-tête.

En tout cas, une variable globale est toujours une cause de problèmes.
05/08/2016, 02h25
emmesse

j'ai compris ce qu'il s'est passé: on ne peut pas mettre des variables (ici des tableaux) dans un fichier d'entête et de #include "fichier.hpp (avec des variables)" dans plus d'un autre fichier.
05/08/2016, 10h05
ternel

Pour l'explication précise, il faut comprendre comment fonctionne la compilation en C++.

Chaque fichier .cpp est compilé indépendamment. lors de l'étape de "preprocess", le compilateur exécute les commandes #..., notamment les #include sont remplacé par le contenu du fichier désigné. La prochaine ligne analysée est la première du fichier fraichement injecté.
L'ensemble forme une unité de traduction, qui est compilée hors de tout contexte.

Lorsque tu places une ligne de code dans un en-tête, elle sera dupliquée dans chaque unité de traduction l'incluant (à chaque inclusion, sauf si on met une garde).
Quand il s'agit d'une déclaration, tout va bien, mais les définitions ne doivent pas être dupliquées (sauf cas particuliers: les définitions de type, et les fonctions inline)

L'erreur ne sera vu qu'à l'édition de liens, c'est à dire quand le programme est complètement compilé et qu'il ne reste plus qu'à relier les morceaux.