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scripts/qapi-types.py: Add dummy member to empty structs

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Make sure that all generated C structs have at least one field; this
avoids potential issues with attempting to malloc space for
zero-length structs in C (g_malloc(sizeof struct) would return NULL).
It also avoids an incompatibility with C++ (where an empty struct is
size 1); that isn't important to us now but might be in future.

Generated empty structures look like this:
    struct Abort
    {
        char qapi_dummy_field_for_empty_struct;
    };

This silences clang warnings like:
./qapi-types.h:3752:1: warning: empty struct has size 0 in C, size 1 in C++ [-Wextern-c-compat]
struct Abort
^

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1419359069-16611-1-git-send-email-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2015-01-20 15:19:32 +00:00
parent a5bd4470ed
commit 83ecb22ba2
1 changed files with 8 additions and 0 deletions
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8
scripts/qapi-types.py
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@ -99,6 +99,14 @@ struct %(name)s
ret += generate_struct_fields(members)
# Make sure that all structs have at least one field; this avoids
# potential issues with attempting to malloc space for zero-length structs
# in C, and also incompatibility with C++ (where an empty struct is size 1).
if not base and not members:
ret += mcgen('''
char qapi_dummy_field_for_empty_struct;
''')
if len(fieldname):
fieldname = " " + fieldname
ret += mcgen('''