gcc ignore casing of symbol names while linking

Question

A software I am working on ships with NETLIB BLAS/LAPACK embedded into its sources using all-lowercase symbol names but now while porting the application to windows I discovered that Intel MKL and several other BLAS/LAPACK implementations for this platform use all-uppercase symbol names. Is there a way to tell the gnu compiler/linker to ignore case while matching symbol names?

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undefined reference to `_dgeqp3'
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$ nm /lib/LAPACK.lib | grep -i " T _dgeqp3"
00000000 T _DGEQP3

Answer 1

I think you might be in for some trouble. Section 6.4.2.1 of the C spec says "Lowercase and uppercase letters are distinct" with respect to identifiers. That means that as far as your compiler and linker are concerned, _DGEQP3 and _dgeqp3 are different symbols. You can probably add some #define statements in a platform-specific header to line things up for you.

Is it because you're linking against a windows library rather than whatever you were using before that this bug showed up?

Answer 2

t.c

#define __CONCAT(x,y) x##y

#ifdef SUFFIX
#define __SUFFIX(x) __CONCAT(x,_)
#else
#define __SUFFIX(x) x
#endif

#ifdef UPPER
#define __c(U,l) __SUFFIX(U)
#else
#define __c(U,l) __SUFFIX(l)
#endif

#define xaxpy __c(XAXPY, xaxpy)

#include <stdio.h>

char* xaxpy;
char* DAXPY;

int main()
{
    printf(xaxpy);
    printf(DAXPY);
}

e.c

char* xaxpy  = "ln";
char* xaxpy_ = "ls";
char* XAXPY  = "UN";
char* XAXPY_ = "US";

there seems to be a way to introduce symbol aliases at link-time using --defsym:

Cetin@BAKA-CHAN ~
$ gcc -D UPPER -D SUFFIX -c t.c e.c

Cetin@BAKA-CHAN ~
$ gcc -o t t.o e.o -Wl,--defsym=_DAXPY=_xaxpy

Cetin@BAKA-CHAN ~
$ ./t
USln
Cetin@BAKA-CHAN ~
$

There must also be a way to give the linker different scripts to handle a large number of such symbol definitions. So I could make it part of the build process to automatically create linker scripts that create mappings between different cases.

Answer 3

The difference you're seeing is due to Fortran calling conventions: in Fortran, symbol case is unimportant, and thus every compiler has a way to translate Fortran symbol names into assembler symbol names: GNU compilers usually translate all to lowercase, Intel on Windows goes for uppercase.

If you're working with Fortran code, you can use the -fsymbol-case-upper option on the older g77 compiler (the newer gfortran compiler doesn't have this). Otherwise, no simple answer for C, except:

• using #define's
• using the C interfaces to BLAS and LAPACK.