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Thread: ECPG: "char*" instead of "const char*" in ecpglib.h

ECPG: "char*" instead of "const char*" in ecpglib.h

From
Tomasz Ostrowski
Date:
Using "char*" as an argument type instead of "const char*" in ecpglib.h
causes that for example the following sample program, basically
copied from docmentation
http://www.postgresql.org/docs/8.1/interactive/ecpg-dynamic.html ,
does not compile using "gcc-4.0.1":

test.pgc

    #include <stdio.h>

    int main()
    {
        EXEC SQL BEGIN DECLARE SECTION;
        const char *select_version_sql = "select version()";
        char version[1000];
        EXEC SQL END DECLARE SECTION;

        EXEC SQL CONNECT TO template1 USER postgres;
        EXEC SQL PREPARE select_version FROM :select_version_sql;
        EXEC SQL EXECUTE select_version INTO :version;
        printf("%s\n", version);
        return 0;
    }

$ ecpg --version
ecpg (PostgreSQL 8.1.0) 4.1.1

$ecpg test.pgc

$gcc test.c -lecpg
test.pgc: In function 'main':
test.pgc:11: warning: passing argument 3 of 'ECPGprepare' discards qualifiers from pointer target type

$g++ test.c -lecpg
test.pgc: In function 'int main()':
test.pgc:11: error: invalid conversion from 'const char*' to 'char*'
test.pgc:11: error:   initializing argument 3 of 'bool ECPGprepare(int, char*, char*)'

----------------------------------------------------------

This forces to use terrible workarounds like:

    const char *select_version_sql = "select version()";
    int select_version_sql_l = strlen(select_version_sql);
    EXEC SQL BEGIN DECLARE SECTION;
    char _select_version_sql[select_version_sql_l+1];
    EXEC SQL END DECLARE SECTION;
    strncpy(_select_version_sql, select_version_sql, select_version_sql_l+1);

    EXEC SQL PREPARE select_version FROM :_select_version_sql;

----------------------------------------------------------

This bug was present in 8.0.4 and is present in 8.1.0 - I haven't
checked other versions.


Is this just a function declaration bug or do ecpg functions really
change their arguments so they cannot be declared "const" (also a bug)?

Regards
Tometzky
--
...although Eating Honey was a very good thing to do, there was a
moment just before you began to eat it which was better than when you
were...
                                                      Winnie the Pooh

Re: ECPG: "char*" instead of "const char*" in ecpglib.h

From
Qingqing Zhou
Date:
On Wed, 9 Nov 2005, Tomasz Ostrowski wrote:
>
> Using "char*" as an argument type instead of "const char*" in ecpglib.h
> causes that for example the following sample program, basically
> copied from docmentation
> http://www.postgresql.org/docs/8.1/interactive/ecpg-dynamic.html ,
> does not compile using "gcc-4.0.1":
>
> $g++ test.c -lecpg
> test.pgc: In function 'int main()':
> test.pgc:11: error: invalid conversion from 'const char*' to 'char*'
> test.pgc:11: error:   initializing argument 3 of 'bool ECPGprepare(int, char*, char*)'
>

Agreed. A patch has been submitted to pg-patches.

Regards,
Qingqing