[sdcc-devel] [ sdcc-Support Requests-1586760 ] SDCC Warning 187 occurs in malloc.h

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Support Requests item #1586760, was opened at 2006-10-29 17:17
Message generated for change (Comment added) made by bnollmeyer
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Category: None
Group: None
Status: Closed
Priority: 5
Private: No
Submitted By: BNOLL (bnollmeyer)
Assigned to: Maarten Brock (maartenbrock)
Summary: SDCC Warning 187 occurs in malloc.h

Initial Comment:
Since Version 2.6 SDCC is reporting a warning 187: ISO
C90 does not support flexible array members. The
warning is related to malloc.h.

The warning can be reproduced by using itoa, atoi, ltoa
... so please have a try.

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>Comment By: BNOLL (bnollmeyer)
Date: 2006-10-30 19:43

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Thanks Maarten, please let me know the changes in malloc.h

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Comment By: Maarten Brock (maartenbrock)
Date: 2006-10-29 20:01

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Fixed in SDCC 2.6.1 #4443.

The option --std-c99 means do not accept SDCC specific keywords like xdata, but only the C99 reserved keywords with 
leading double underscores like __xdata. It also means to accept C99 extensions to C90.

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Comment By: Maarten Brock (maartenbrock)
Date: 2006-10-29 19:35

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In general malloc tends to fragment the already limited memory. After a while it will no longer be able to allocate 
the requested memory. It is much safer to statically allocate the expected memory usage. But of course in the end 
it is the users choice.

I'll fix the header file though as the struct defined in there is not to be used by the user.

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Comment By: Nobody/Anonymous (nobody)
Date: 2006-10-29 19:12

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In general it is not recommended to use malloc in a small
embedded system in the first place.

Mmmh, if you try itoa, ltoa by using the SDCC LIB, malloc.h
will we included by these functions. However, the warning is
new since Version 2.6.

--std-sdcc99 works fine, the other given option produces
even more errors.

Please explain the difference between V2.5, V2.6 in that
specific case.

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Comment By: Jesus Calvino-Fraga (jesusc)
Date: 2006-10-29 18:57

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>In general it is not recommended to use malloc in a small
embedded system in the first place.

Why?  That is for the user to decide, not the compiler.  I recently used 
malloc/realloc/free in a 8051 program and it worked extremelly well! In fact, I used 
working code compiled with MSVC and easily ported it to sdcc.  With malloc() one can 
really take advantage of the limited memory of an embedded system.

Jesus
  

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Comment By: Philipp Krause (spth)
Date: 2006-10-29 18:02

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Warning exist to warn the user that he's likely to have done
something wrong. Warnings caused by compiler internals, such
as the implementation of malloc.h are not helpful, they just
distract from the warnings that have meaning to the user.


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Comment By: Maarten Brock (maartenbrock)
Date: 2006-10-29 17:53

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And the question is...?

In general it is not recommended to use malloc in a small embedded system in the first place.

And allthough C90 does not support flexible array members, SDCC handles them perfectly.
If you compile with --std-c99 or --std-sdcc99 you will not get the warning.

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