Using define macro and its value in quotes
Writing some C code just out of curiosity and I'd like to move some values for a MySQL connection to a kind of const.
Question 1
Is it a good idea to store host, user etc in preprocessor macros? I.e.:
#include <my_global.h>
#include <mysql.h>
#define DB_HOST "mysqlhost.com"
#define DB_USER "mysqlusername"
#define DB_TABLE "tablename"
...
To use them later like mysql_real_connect(con, DB_HOST, DB_USER, DP_PASS, DB_NAME, 0, NULL, 0) == NULL)
?
Question 2
Can I use DB_TABLE's value inside a quoted string? I.e. mysql_query(con, "SELECT * FROM DB_TABLE")
If so - what is corrcect way to use it here?
c macros preprocessor-directive
edited Jan 25 at 10:58
alk
59k764177
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
add a comment |
Writing some C code just out of curiosity and I'd like to move some values for a MySQL connection to a kind of const.
Question 1
Is it a good idea to store host, user etc in preprocessor macros? I.e.:
#include <my_global.h>
#include <mysql.h>
#define DB_HOST "mysqlhost.com"
#define DB_USER "mysqlusername"
#define DB_TABLE "tablename"
...
To use them later like mysql_real_connect(con, DB_HOST, DB_USER, DP_PASS, DB_NAME, 0, NULL, 0) == NULL)
?
Question 2
Can I use DB_TABLE's value inside a quoted string? I.e. mysql_query(con, "SELECT * FROM DB_TABLE")
If so - what is corrcect way to use it here?
c macros preprocessor-directive
edited Jan 25 at 10:58
alk
59k764177
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
2
Regarding the first question, check this answer about the advantages of const vs define (vs enum): stackoverflow.com/a/1674459/7520531
– Jose
Jan 25 at 11:11
add a comment |
Writing some C code just out of curiosity and I'd like to move some values for a MySQL connection to a kind of const.
Question 1
Is it a good idea to store host, user etc in preprocessor macros? I.e.:
#include <my_global.h>
#include <mysql.h>
#define DB_HOST "mysqlhost.com"
#define DB_USER "mysqlusername"
#define DB_TABLE "tablename"
...
To use them later like mysql_real_connect(con, DB_HOST, DB_USER, DP_PASS, DB_NAME, 0, NULL, 0) == NULL)
?
Question 2
Can I use DB_TABLE's value inside a quoted string? I.e. mysql_query(con, "SELECT * FROM DB_TABLE")
If so - what is corrcect way to use it here?
c macros preprocessor-directive
edited Jan 25 at 10:58
alk
59k764177
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
Writing some C code just out of curiosity and I'd like to move some values for a MySQL connection to a kind of const.
Question 1
Is it a good idea to store host, user etc in preprocessor macros? I.e.:
#include <my_global.h>
#include <mysql.h>
#define DB_HOST "mysqlhost.com"
#define DB_USER "mysqlusername"
#define DB_TABLE "tablename"
...
To use them later like mysql_real_connect(con, DB_HOST, DB_USER, DP_PASS, DB_NAME, 0, NULL, 0) == NULL)
?
Question 2
Can I use DB_TABLE's value inside a quoted string? I.e. mysql_query(con, "SELECT * FROM DB_TABLE")
If so - what is corrcect way to use it here?
c macros preprocessor-directive
c macros preprocessor-directive
edited Jan 25 at 10:58
alk
59k764177
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
edited Jan 25 at 10:58
alk
59k764177
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
edited Jan 25 at 10:58
alk
59k764177
edited Jan 25 at 10:58
alk
59k764177
edited Jan 25 at 10:58
alk
59k764177
59k764177
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
asked Jan 25 at 10:48
setevoysetevoy
1,56343053
1,56343053
2
Regarding the first question, check this answer about the advantages of const vs define (vs enum): stackoverflow.com/a/1674459/7520531
– Jose
Jan 25 at 11:11
add a comment |
2
Regarding the first question, check this answer about the advantages of const vs define (vs enum): stackoverflow.com/a/1674459/7520531
– Jose
Jan 25 at 11:11
2
2
Regarding the first question, check this answer about the advantages of const vs define (vs enum): stackoverflow.com/a/1674459/7520531
– Jose
Jan 25 at 11:11
Regarding the first question, check this answer about the advantages of const vs define (vs enum): stackoverflow.com/a/1674459/7520531
– Jose
Jan 25 at 11:11
add a comment |
2 Answers
2
active
oldest
votes
Answer 1: Technically, you can define it the way you have shown, but at times, it makes sense to make the parameters which are likely to change (like hostname, username) as environment variables, and read them during the program execution. This makes your program more robust against frequent changes. The parameters which are to remain same, can surely be used as a #define preprocessor (like tablename).
A sample can be found here.
Answer 2: No, you cannot use it like that. However, since pre-processor MACROS are compile time substitution, you can take advantage of string concatenation, like
mysql_query(con, "SELECT * FROM " DB_TABLE);
where DB_TABLE is defined as a MACRO.
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
add a comment |
Is it a good idea to store host, user etc in preprocessor macros?
It is common practise, at least if the values can be considered constant in the context of the program.
Alternatively you can define constants by doing:
const char * db_host = "localhost";
The drawback here is that the simple concatenation as shown below won't work.
Can I use
DB_TABLE's value inside a quoted string?
No, but you can just do:
mysql_query(con, "SELECT * FROM " DB_TABLE);
answered Jan 25 at 10:51
alkalk
59k764177
Dont you think the second answer ought to start with "No...."...?
– Sourav Ghosh
Jan 25 at 10:54
@SouravGhosh: Absolutely!
– alk
Jan 25 at 10:55
1
I don't think that is common practice to store values such as hostname and username in MACROS! ... It's common for very small applications ... ;)
– Sir Jo Black
Jan 25 at 10:58
2
@SirJoBlack: Well I, generalised the question to whether it were common to #define strings. If to do so for host or user names made sense at least depends .... Reworded my answer.
– alk
Jan 25 at 11:02
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Answer 1: Technically, you can define it the way you have shown, but at times, it makes sense to make the parameters which are likely to change (like hostname, username) as environment variables, and read them during the program execution. This makes your program more robust against frequent changes. The parameters which are to remain same, can surely be used as a #define preprocessor (like tablename).
A sample can be found here.
Answer 2: No, you cannot use it like that. However, since pre-processor MACROS are compile time substitution, you can take advantage of string concatenation, like
mysql_query(con, "SELECT * FROM " DB_TABLE);
where DB_TABLE is defined as a MACRO.
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
add a comment |
Answer 1: Technically, you can define it the way you have shown, but at times, it makes sense to make the parameters which are likely to change (like hostname, username) as environment variables, and read them during the program execution. This makes your program more robust against frequent changes. The parameters which are to remain same, can surely be used as a #define preprocessor (like tablename).
A sample can be found here.
Answer 2: No, you cannot use it like that. However, since pre-processor MACROS are compile time substitution, you can take advantage of string concatenation, like
mysql_query(con, "SELECT * FROM " DB_TABLE);
where DB_TABLE is defined as a MACRO.
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
add a comment |
Answer 1: Technically, you can define it the way you have shown, but at times, it makes sense to make the parameters which are likely to change (like hostname, username) as environment variables, and read them during the program execution. This makes your program more robust against frequent changes. The parameters which are to remain same, can surely be used as a #define preprocessor (like tablename).
A sample can be found here.
Answer 2: No, you cannot use it like that. However, since pre-processor MACROS are compile time substitution, you can take advantage of string concatenation, like
mysql_query(con, "SELECT * FROM " DB_TABLE);
where DB_TABLE is defined as a MACRO.
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
Answer 1: Technically, you can define it the way you have shown, but at times, it makes sense to make the parameters which are likely to change (like hostname, username) as environment variables, and read them during the program execution. This makes your program more robust against frequent changes. The parameters which are to remain same, can surely be used as a #define preprocessor (like tablename).
A sample can be found here.
Answer 2: No, you cannot use it like that. However, since pre-processor MACROS are compile time substitution, you can take advantage of string concatenation, like
mysql_query(con, "SELECT * FROM " DB_TABLE);
where DB_TABLE is defined as a MACRO.
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
edited Jan 25 at 12:12
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
answered Jan 25 at 10:54
Sourav GhoshSourav Ghosh
110k14130189
110k14130189
add a comment |
add a comment |
Is it a good idea to store host, user etc in preprocessor macros?
It is common practise, at least if the values can be considered constant in the context of the program.
Alternatively you can define constants by doing:
const char * db_host = "localhost";
The drawback here is that the simple concatenation as shown below won't work.
Can I use
DB_TABLE's value inside a quoted string?
No, but you can just do:
mysql_query(con, "SELECT * FROM " DB_TABLE);
answered Jan 25 at 10:51
alkalk
59k764177
Dont you think the second answer ought to start with "No...."...?
– Sourav Ghosh
Jan 25 at 10:54
@SouravGhosh: Absolutely!
– alk
Jan 25 at 10:55
1
I don't think that is common practice to store values such as hostname and username in MACROS! ... It's common for very small applications ... ;)
– Sir Jo Black
Jan 25 at 10:58
2
@SirJoBlack: Well I, generalised the question to whether it were common to #define strings. If to do so for host or user names made sense at least depends .... Reworded my answer.
– alk
Jan 25 at 11:02
add a comment |
Is it a good idea to store host, user etc in preprocessor macros?
It is common practise, at least if the values can be considered constant in the context of the program.
Alternatively you can define constants by doing:
const char * db_host = "localhost";
The drawback here is that the simple concatenation as shown below won't work.
Can I use
DB_TABLE's value inside a quoted string?
No, but you can just do:
mysql_query(con, "SELECT * FROM " DB_TABLE);
answered Jan 25 at 10:51
alkalk
59k764177
Dont you think the second answer ought to start with "No...."...?
– Sourav Ghosh
Jan 25 at 10:54
@SouravGhosh: Absolutely!
– alk
Jan 25 at 10:55
1
I don't think that is common practice to store values such as hostname and username in MACROS! ... It's common for very small applications ... ;)
– Sir Jo Black
Jan 25 at 10:58
2
@SirJoBlack: Well I, generalised the question to whether it were common to #define strings. If to do so for host or user names made sense at least depends .... Reworded my answer.
– alk
Jan 25 at 11:02
add a comment |
Is it a good idea to store host, user etc in preprocessor macros?
It is common practise, at least if the values can be considered constant in the context of the program.
Alternatively you can define constants by doing:
const char * db_host = "localhost";
The drawback here is that the simple concatenation as shown below won't work.
Can I use
DB_TABLE's value inside a quoted string?
No, but you can just do:
mysql_query(con, "SELECT * FROM " DB_TABLE);
answered Jan 25 at 10:51
alkalk
59k764177
Is it a good idea to store host, user etc in preprocessor macros?
It is common practise, at least if the values can be considered constant in the context of the program.
Alternatively you can define constants by doing:
const char * db_host = "localhost";
The drawback here is that the simple concatenation as shown below won't work.
Can I use
DB_TABLE's value inside a quoted string?
No, but you can just do:
mysql_query(con, "SELECT * FROM " DB_TABLE);
answered Jan 25 at 10:51
alkalk
59k764177
edited Jan 25 at 11:03
answered Jan 25 at 10:51
alkalk
59k764177
answered Jan 25 at 10:51
alkalk
59k764177
answered Jan 25 at 10:51
alkalk
59k764177
59k764177
Dont you think the second answer ought to start with "No...."...?
– Sourav Ghosh
Jan 25 at 10:54
@SouravGhosh: Absolutely!
– alk
Jan 25 at 10:55
1
I don't think that is common practice to store values such as hostname and username in MACROS! ... It's common for very small applications ... ;)
– Sir Jo Black
Jan 25 at 10:58
2
@SirJoBlack: Well I, generalised the question to whether it were common to #define strings. If to do so for host or user names made sense at least depends .... Reworded my answer.
– alk
Jan 25 at 11:02
add a comment |
Dont you think the second answer ought to start with "No...."...?
– Sourav Ghosh
Jan 25 at 10:54
@SouravGhosh: Absolutely!
– alk
Jan 25 at 10:55
1
I don't think that is common practice to store values such as hostname and username in MACROS! ... It's common for very small applications ... ;)
– Sir Jo Black
Jan 25 at 10:58
2
@SirJoBlack: Well I, generalised the question to whether it were common to #define strings. If to do so for host or user names made sense at least depends .... Reworded my answer.
– alk
Jan 25 at 11:02
Dont you think the second answer ought to start with "No...."...?
– Sourav Ghosh
Jan 25 at 10:54
Dont you think the second answer ought to start with "No...."...?
– Sourav Ghosh
Jan 25 at 10:54
@SouravGhosh: Absolutely!
– alk
Jan 25 at 10:55
@SouravGhosh: Absolutely!
– alk
Jan 25 at 10:55
1
1
I don't think that is common practice to store values such as hostname and username in MACROS! ... It's common for very small applications ... ;)
– Sir Jo Black
Jan 25 at 10:58
I don't think that is common practice to store values such as hostname and username in MACROS! ... It's common for very small applications ... ;)
– Sir Jo Black
Jan 25 at 10:58
2
2
@SirJoBlack: Well I, generalised the question to whether it were common to #define strings. If to do so for host or user names made sense at least depends .... Reworded my answer.
– alk
Jan 25 at 11:02
@SirJoBlack: Well I, generalised the question to whether it were common to #define strings. If to do so for host or user names made sense at least depends .... Reworded my answer.
– alk
Jan 25 at 11:02
add a comment |
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2
Regarding the first question, check this answer about the advantages of const vs define (vs enum): stackoverflow.com/a/1674459/7520531
– Jose
Jan 25 at 11:11