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CheckSymbolExists: force the compiler to keep the referenced symbol 

Otherwise the compiler may optimize out the reference to the symbol as the
previous version was not really using this. This leads to symbols that are
only in a header but not in the given libraries to be reported as present.

This came up on the first try to fix bug 11333 as "gcc -O3" would optimize
out the reference to pthread_create() so the correct library the symbol is in
was not detected.

The new test code was suggested by Brad King.
This commit is contained in:
Rolf Eike Beer 2012-01-03 19:54:43 +01:00
parent 9a20abf04a
commit 813eca6416
1 changed files with 1 additions and 1 deletions
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2
Modules/CheckSymbolExists.cmake
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@ -60,7 +60,7 @@ MACRO(_CHECK_SYMBOL_EXISTS SOURCEFILE SYMBOL FILES VARIABLE)
"${CMAKE_CONFIGURABLE_FILE_CONTENT}#include <${FILE}>\n") "${CMAKE_CONFIGURABLE_FILE_CONTENT}#include <${FILE}>\n")
ENDFOREACH(FILE) ENDFOREACH(FILE)
SET(CMAKE_CONFIGURABLE_FILE_CONTENT SET(CMAKE_CONFIGURABLE_FILE_CONTENT
"${CMAKE_CONFIGURABLE_FILE_CONTENT}\nvoid cmakeRequireSymbol(int dummy,...){(void)dummy;}\nint main()\n{\n#ifndef ${SYMBOL}\n cmakeRequireSymbol(0,&${SYMBOL});\n#endif\n return 0;\n}\n") "${CMAKE_CONFIGURABLE_FILE_CONTENT}\nint main(int argc, char** argv)\n{\n (void)argv;\n#ifndef ${SYMBOL}\n return ((int*)(&${SYMBOL}))[argc];\n#else\n (void)argc;\n return 0;\n#endif\n}\n")
CONFIGURE_FILE("${CMAKE_ROOT}/Modules/CMakeConfigurableFile.in" CONFIGURE_FILE("${CMAKE_ROOT}/Modules/CMakeConfigurableFile.in"
"${SOURCEFILE}" @ONLY IMMEDIATE) "${SOURCEFILE}" @ONLY IMMEDIATE)