<strings.h> ffs probably used to work by accident on x86 #439
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hubot
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<strings.h>'s ffs used to work by accident. In the past, <strings.h> used to incorrectly declare ffs for all platforms at all API levels. In the unified headers, there's no such declaration for x86 before API 18 (which makes sense, because that function was missing on x86 until then). But as long as there was a declaration for ffs, the compiler just inlined __builtin_ffs. There was no problem at link time because the compiler didn't actually add a reference to the missing ffs symbol. Restore the old behavior by manually instructing the compiler to inline its builtin in these cases. Bug: android/ndk#439 Test: built new NDK 'ffs' test Change-Id: I840e99f237c86f7cb028a0f67aaa8c6ff3eda245
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danalbert cherrypicked this for r15c, so marking closed. |
miodragdinic
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This test requires <android/legacy_strings_inlines.h>. Bug: android/ndk#439 Test: ./run_tests.py --filter ffs --rebuild --toolchain clang --ndk /usr/local/google/android-ndk-hacked Change-Id: I2e6ee1daeca626e0ba739374f4b662ac61438a63
sepehrst
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<strings.h>'s ffs used to work by accident. In the past, <strings.h> used to incorrectly declare ffs for all platforms at all API levels. In the unified headers, there's no such declaration for x86 before API 18 (which makes sense, because that function was missing on x86 until then). But as long as there was a declaration for ffs, the compiler just inlined __builtin_ffs. There was no problem at link time because the compiler didn't actually add a reference to the missing ffs symbol. Restore the old behavior by manually instructing the compiler to inline its builtin in these cases. Bug: android/ndk#439 Test: built new NDK 'ffs' test Change-Id: I840e99f237c86f7cb028a0f67aaa8c6ff3eda245
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we had an internal report of someone having trouble building some ffs-using code for x86 after they upgraded to r15b. i suspect this was because of the switch to unified headers. in the past, strings.h used to declare ffs for all platforms at all API levels. in the more correct unified headers, there's no such declaration for x86 before API 18.
but --- i think as long as there was a declaration the compiler will have just said "ffs? i know ffs!" and inlined
__builtin_ffsand not had any problem at link-time because it wasn't actually adding a reference to the missing symbol.i think we should probably add a <android/legacy_strings_inlines.h> with a
static inlinethat just calls__builtin_ffs(which is all the libc ffs is anyway).The text was updated successfully, but these errors were encountered: