GCC can emit prologue/epilogue code for the functions in various different cases: - frame pointers - PIC build (to load ebx for indirect calls/jumps) - forced stack smashing protection If we used jump in such cases, we'd corrupt the call stack and crash. Signed-off-by: Timo Teräs --- libm/ldouble_wrappers.c | 12 +++++++----- 1 files changed, 7 insertions(+), 5 deletions(-) diff --git a/libm/ldouble_wrappers.c b/libm/ldouble_wrappers.c index 7d5af90..5b424dc 100644 --- a/libm/ldouble_wrappers.c +++ b/libm/ldouble_wrappers.c @@ -60,7 +60,9 @@ long long func##l(long double x) \ * The return value is returned in st(0) per ABI in both cases (returning * a long double or returning a double). So we can simply jump to func. * Using __GI_func in jump to make optimized intra-library jump. - * gcc will still generate a useless "ret" after asm. Oh well... + * + * We do need to use call (instead of tail jump) as gcc can create + * stack frame, and push/modify/pop ebx during PIC build. */ # define WRAPPER1(func) \ long double func##l(long double x) \ @@ -69,7 +71,7 @@ long double func##l(long double x) \ __asm ( \ " fldt %1\n" \ " fstpl %1\n" \ - " jmp " __stringify(__GI_##func) "\n" \ + " call " __stringify(__GI_##func) "\n" \ : "=t" (st_top) \ : "m" (x) \ ); \ @@ -82,7 +84,7 @@ int func##l(long double x) \ __asm ( \ " fldt %1\n" \ " fstpl %1\n" \ - " jmp " __stringify(__GI_##func) "\n" \ + " call " __stringify(__GI_##func) "\n" \ : "=a" (ret) \ : "m" (x) \ ); \ @@ -95,7 +97,7 @@ long func##l(long double x) \ __asm ( \ " fldt %1\n" \ " fstpl %1\n" \ - " jmp " __stringify(__GI_##func) "\n" \ + " call " __stringify(__GI_##func) "\n" \ : "=a" (ret) \ : "m" (x) \ ); \ @@ -108,7 +110,7 @@ long long func##l(long double x) \ __asm ( \ " fldt %1\n" \ " fstpl %1\n" \ - " jmp " __stringify(__GI_##func) "\n" \ + " call " __stringify(__GI_##func) "\n" \ : "=A" (ret) \ : "m" (x) \ ); \ -- 1.7.0.4